Mikrotik-Total-Limit attribute Not working.

Respected All, I use Mikrotik-Total-Limit attribute for send a remain data of user in radreply.But that is only working upto 9 GB or something. I try to google for that and i found new attribute Mikrotik-Total-Limit-Gigawords. But also that is like puzzle.When i send Mikrotik-Total-Limit = 2 than that shows 12 GB and when i send 10 than that shows just random number every time. Warm Regard's Imdadali Kadiwala