Critical bug

I like your plugin very much, but there is a big problem with it.
That points is endless… For example:
1. Client get 5% from cost of product.
2. Client buys product for 1000 USD.
3. Order is closed.
4. Client gets 50 points.
5. Client want to buy product for 500 USD.
6. Client uses his 50 points, – price is 450 USD.
7. Order is closed.

And guess what is points balance… It must be 22,5 USD, but instead we get 72,5 USD.
It means that points are endless…