If Jane introduces a customer who purchases $100 worth. She earns $30 credit (30%).
Once Jane makes $500 in sales, she has $150 credit (30%).
When credit reaches $150, it can be converted into $75 cash that can be sent to any account she wants.
If Joe referred us Jane
And Jane referred customers who bought $500 (in last example).
Joe earns $30 in credit since Jane earns $150 credit (20% of $150).