User Manager Download Limitation Problem

Dear All
I have a problem with mikrotik user manager transfer limitation, I set 50m limitation to each client but when client download a 200m file, user manager allow and when download is finished expire client user account, I think that user manager work in session mode, but i would like it disconnect client download in exactly 50m no in finish file size.
please help me.

mmm…

fascinating…

its hotspot or ppp ??