Improved documentation for BUILD_CONST_KEY_MAP (GH-19454)

Author: laike9m

Doc/library/dis.rst

@@ -844,9 +844,9 @@ All of the following opcodes use their arguments.
 
 .. opcode:: BUILD_CONST_KEY_MAP (count)
 
-   The version of :opcode:`BUILD_MAP` specialized for constant keys.  *count*
-   values are consumed from the stack.  The top element on the stack contains
-   a tuple of keys.
+   The version of :opcode:`BUILD_MAP` specialized for constant keys. Pops the
+   top element on the stack which contains a tuple of keys, then starting from
+   ``TOS1``, pops *count* values to form values in the built dictionary.
 
    .. versionadded:: 3.6