Note: I do not have a ChatGPT Team account so can only infer from what I know from this post.
The limit of users is 999 based on what can be entered in the setup page for ChatGPT Team.
Now if there were 999 users each asking just one question in one hour, then many would not be able to ask any questions if the limit was 100 messages per 3 hours for all Team members combined and the forum would surely be flamming with negative post if that were true.
So I would safely conclude that it is 100 messages per 3 hours per User of a Team. 