In a co-working space, some of my users signup for daily 6 hours or 8 hours package. I wanted to give them like 6 hrs * 26 days = 156 hours or say 208 hrs in total. and let them use any number of hours per day, once total 156 / 208 hours ends they should not be able to have net access. They may use pattern like 4 hours 1st then go home, then 8 hour next day, so total time consumed should be like 12 hours. but no matter what combination i try, permanant / scheduled / by time / by client / voucher duration / client duration but in all combos following happens.

1st day : used 4 hours and left home - > time pauses at 4 hours duration - > perfectly fine. 

2nd day : The moment he comes and connects (automatically) to same SSID, all off line time just adds up to his duration, meaning suppose he comes back after 16 hours, the moment he connects (automatically) duration become 20 hrs (4hr used and 16 hrs of offline) and then starts counting from 20 hours.

Please help, how can i set such vouchers and stop off line times to be added up.

Regards