simplify block range request description

There's room for ambiguity as to what `count` means - this clarifies
that it always relates to the slot, and not the number of blocks in the
response which allows clients to request ranges epoch by epoch (for
example) without worrying about overlaps caused by empty slots.

specs/phase0/p2p-interface.md

@@ -463,7 +463,7 @@ Snappy has two formats: "block" and "frames" (streaming). To support large reque
 Since snappy frame contents [have a maximum size of `65536` bytes](https://github.com/google/snappy/blob/master/framing_format.txt#L104)
  and frame headers are just `identifier (1) + checksum (4)` bytes, the expected buffering of a single frame is acceptable.
 
-**Encoding-dependent header:** Req/Resp protocols using the `ssz` or `ssz_snappy` encoding strategies MUST encode the length of the raw SSZ bytes, encoded as an unsigned [protobuf varint](https://developers.google.com/protocol-buffers/docs/encoding#varints). 
+**Encoding-dependent header:** Req/Resp protocols using the `ssz` or `ssz_snappy` encoding strategies MUST encode the length of the raw SSZ bytes, encoded as an unsigned [protobuf varint](https://developers.google.com/protocol-buffers/docs/encoding#varints).
 
 *Writing*: By first computing and writing the SSZ byte length, the SSZ encoder can then directly write the chunk contents to the stream.
 If Snappy is applied, it can be passed through a buffered Snappy writer to compress frame by frame.
@@ -577,7 +577,7 @@ Response Content:
 )
 ```
 
-Requests count beacon blocks from the peer starting from `start_slot`, leading up to the current head block as selected by fork choice. `step` defines the slot increment between blocks. For example, requesting blocks starting at `start_slot` 2 with a step value of 2 would return the blocks at slots [2, 4, 6, …]. In cases where a slot is empty for a given slot number, no block is returned. For example, if slot 4 were empty in the previous example, the returned array would contain [2, 6, …]. A step value of 1 returns all blocks on the range `[start_slot, start_slot + count)`.
+Requests beacon blocks in the slot range `[start_slot, start_slot + count * step)`], leading up to the current head block as selected by fork choice. `step` defines the slot increment between blocks. For example, requesting blocks starting at `start_slot` 2 with a step value of 2 would return the blocks at slots [2, 4, 6, …]. In cases where a slot is empty for a given slot number, no block is returned. For example, if slot 4 were empty in the previous example, the returned array would contain [2, 6, …].
 
 `BeaconBlocksByRange` is primarily used to sync historical blocks.