* "That's about it" - This means that you have finished talking about something, or you have explained everything you need to. It indicates completion or finality.
* "What about that?" - This is a question expressing surprise, amusement, or disapproval regarding something that has just been said or done. It can also be used to emphasize a point.
* "What's that about?" - This is a question seeking clarification or explanation about something that is unclear or surprising.
If you can provide more context about where you encountered the phrase "that about," I may be able to give you a more specific answer.