diff --git a/CHANGES.rst b/CHANGES.rst
index 47245386f2..eda0bae286 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -108,7 +108,7 @@ Bug Fixes
 - Prevent duplicate labels by changing duplicate number appended
   to label to max number (of duplicates) plus 1. [#1824]
 
-- Layer lettering now supports up to 700 layers. [#1850]
+- Layer lettering now supports up to 702 layers. Beyond that, special characters are used. [#1850]
 
 Cubeviz
 ^^^^^^^
diff --git a/jdaviz/utils.py b/jdaviz/utils.py
index e94d9313f0..7585ea4e12 100644
--- a/jdaviz/utils.py
+++ b/jdaviz/utils.py
@@ -176,17 +176,18 @@ def bqplot_clear_figure(fig):
 
 
 def alpha_index(index):
-    """Converts an index to A-Z, AA-ZZ
+    """Converts an index to label (A-Z, AA-ZZ).
 
     Parameters
     ----------
-    index : Integer
-        index between 9 and 701
+    index : int
+        Index between 0 and 701, inclusive. Higher number is accepted but
+        will have special characters.
 
     Returns
     -------
-    String
-        String in the range A-Z, AA-ZZ
+    label : str
+        String in the range A-Z, AA-ZZ if index is within 0-701 range, inclusive.
     """
     # if we ever want to support more than 702 layers, then we'll need a third
     # "digit" and will need to account for the horizontal space in the legends