That was the way I read the manual as well. I thought that as soon as the function saw a character meeting the WAIT criteria it would terminate collecting any more characters. In fact what I'm seeing is that it continues to gather all 5 characters, so it collects the comma as well if the string is less than 5!

The manual says the string length is determined by the count OR when the optional character is encountered. Unfortunately that sentence can be interpreted two ways.