When you put multiple users in the same quota target, the quota limits defined by that quota are not applied to each individual user; in this case, the quota limits are shared among all users listed in the quota target.
#Quota target type disk files thold sdisk sfile #---------- ---- ---- ----- ----- ----- ----- jsmith,chen user@/vol/vol1 80MThe two users can use up to 80 MB of space combined. If one uses 75 MB, then the other one can use only 5 MB.