Limit max trafic x user

[AnonymousWebHacker]

Hello, excellent script, I learned several things with it. I hope you can answer me

I have friends who live in countries with blocked internet so I decided to help them by renting a vps and installing vpn.

I pay the VPS fee without problems, but they charge a price if they exceed the monthly traffic of 250 GB.

The idea is that how can I create an example user1, user2 and specify, that each user can consume 125 gb per month?