my forum 'most users ever online' is stuck at 50 and yesterday i had more than 50 visitor, users and guest combined, but the increment was not recorded ....how do i fit this problem

pls i also want to know the criteria for the increment to occur

The Stats are Cached, you can go to the Host Settings (Host Settings -> Cache)and Clear the Cache then the Stats should be updated.

There's another reason - IIS multiplies sessions from the same user and if many users, let's say guests, behind the only NAT it will not be counted too. It can't be fixed.