getPstnCalls tabular response contains a Call ID that is not unique

Question

ID is short for Identifier. An Identifier, by definition, must be unique. Microsoft’s online documentation contradicts itself. In the header info below it states:
Each row maps to one call. One column is the CallID. It states it is not guaranteed to be unique.
This suggests each row does not represent a call but part of a call.
Which is it?