Just to clarify as I've never had someone in two different groups with different values of the same permission.
In this example, I'd have them in Group A or Group B, but not both:
Are you saying that if Group A has an editing time limit of 10 minutes and Group B has one of 20 minutes, and a member is in both, is it cumulative as in a total of 30 minutes,
Or, what I thought due to "never", does the greater of the two apply (Group B with 20 minutes)?
Cumulative - increasing or increased in quantity, degree, or force by successive additions.