diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/aggregator/Sum.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/aggregator/Sum.ts
index 1c0660e7c8..1482841106 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/aggregator/Sum.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/aggregator/Sum.ts
@@ -54,10 +54,12 @@ export class SumAggregator implements Aggregator<SumAccumulation> {
    * Returns the result of the merge of the given accumulations.
    */
   merge(previous: SumAccumulation, delta: SumAccumulation): SumAccumulation {
+    const prevPv = previous.toPointValue();
+    const deltaPv = delta.toPointValue();
     if (delta.reset) {
-      return new SumAccumulation(delta.startTime, this.monotonic, delta.toPointValue(), delta.reset);
+      return new SumAccumulation(delta.startTime, this.monotonic, deltaPv, delta.reset);
     }
-    return new SumAccumulation(previous.startTime, this.monotonic, previous.toPointValue() + delta.toPointValue());
+    return new SumAccumulation(previous.startTime, this.monotonic, prevPv + deltaPv);
   }
 
   /**
@@ -74,7 +76,7 @@ export class SumAggregator implements Aggregator<SumAccumulation> {
     if (this.monotonic && (prevPv > currPv)) {
       return new SumAccumulation(current.startTime, this.monotonic, currPv, true);
     }
-    return new SumAccumulation(current.startTime, this.monotonic, current.toPointValue() - previous.toPointValue());
+    return new SumAccumulation(current.startTime, this.monotonic, currPv - prevPv);
   }
 
   toMetricData(
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/state/DeltaMetricProcessor.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/state/DeltaMetricProcessor.ts
index 3d269cc14b..22c25edab0 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/state/DeltaMetricProcessor.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/state/DeltaMetricProcessor.ts
@@ -49,7 +49,7 @@ export class DeltaMetricProcessor<T extends Maybe<Accumulation>> {
       accumulation?.record(value);
       let delta = accumulation;
       if (this._cumulativeMemoStorage.has(attributes, hashCode)) {
-        // previous must present.
+        // has() returned true, previous is present.
         // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
         const previous = this._cumulativeMemoStorage.get(attributes, hashCode)!;
         delta = this._aggregator.diff(previous, accumulation);
@@ -62,7 +62,7 @@ export class DeltaMetricProcessor<T extends Maybe<Accumulation>> {
   }
 
   /**
-   * Returns a collection of delta metrics. Their start time is the when first
+   * Returns a collection of delta metrics. Start time is the when first
    * time event collected.
    */
   collect() {
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/state/TemporalMetricProcessor.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/state/TemporalMetricProcessor.ts
index de152d58fe..6c648ac117 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/state/TemporalMetricProcessor.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/state/TemporalMetricProcessor.ts
@@ -153,7 +153,7 @@ export class TemporalMetricProcessor<T extends Maybe<Accumulation>> {
       const [key, record, hash] = next.value;
       if (last.has(key, hash)) {
         const lastAccumulation = last.get(key, hash);
-        // lastAccumulation must present.
+        // last.has() returned true, lastAccumulation is present.
         // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
         const accumulation = aggregator.merge(lastAccumulation!, record);
         result.set(key, accumulation, hash);
@@ -167,20 +167,13 @@ export class TemporalMetricProcessor<T extends Maybe<Accumulation>> {
   }
 
   /**
-   * Calibrate the reported metric streams's startTime to lastCollectionTime. Leaves
+   * Calibrate the reported metric streams' startTime to lastCollectionTime. Leaves
    * the new stream to be the initial observation time unchanged.
    */
   static calibrateStartTime<T extends Maybe<Accumulation>>(last: AttributeHashMap<T>, current: AttributeHashMap<T>, lastCollectionTime: HrTime) {
-    const iterator = last.keys();
-    let next = iterator.next();
-    while (next.done !== true) {
-      const [key, hash] = next.value;
-      if (current.has(key, hash)) {
-        const currentAccumulation = current.get(key, hash);
-        currentAccumulation?.setStartTime(lastCollectionTime);
-      }
-
-      next = iterator.next();
+    for (const [key, hash] of last.keys()) {
+      const currentAccumulation = current.get(key, hash);
+      currentAccumulation?.setStartTime(lastCollectionTime);
     }
     return current;
   }
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/test/aggregator/Sum.test.ts b/experimental/packages/opentelemetry-sdk-metrics-base/test/aggregator/Sum.test.ts
index bb456b91d1..ac3df809a6 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/test/aggregator/Sum.test.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/test/aggregator/Sum.test.ts
@@ -70,7 +70,7 @@ describe('SumAggregator', () => {
       const prev = aggregator.createAccumulation([0, 0]);
       prev.record(10);
 
-      // A new record with the value been reset.
+      // Create a new record that indicates a reset.
       const curr = aggregator.createAccumulation([1, 1]);
       curr.record(3);