Urgent Help: RAS’s IP

Tried to make a IP pool for RAS VPN connections. I like to setup 50 VPN client connection starting IP from x.x.x.100(Class C).

I entered IP address as: X.X.X.100
Mas as: X.X.X.192
This is class C.
Then RAS server came up IP Range as: x.x.x.102 To x.x.x.126
Number of address for clients is 63.

Problem: If I user 126-102=24 clients.

Does anyone knows how the RAS calculate the number of IP clients with 63?
Any Expert help me to enter a right Mask for IP x.x.x.100(Nedds 50 clients)
Thank in advance