Yes having the two different constaints shown can be misleading. This comes however from a whole series of 'problems' for users where the only limit shown is the one set in the jD User Groups Settings as many, including administrators, were unaware there is a limit due to the php settings. Also some admins did not notice the limit in the Users Groups Settings.
The quickest fix was to show both.
An enhancement would be to show the lowest together with appropriate text indicating the source of the limitation. Perhaps with a link to the relevant article in the documentation. So I think it is a good idea to move this topic to suggestions.