I'm not sure I understand your question fully, but here's what I understand about the referrals.
Amazon means "sales". So, if you make 7 sales then your sales commission will increase to 6%.
I think they mean MONTHLY. So, you have to make 7 sales each month. For example they count from July 1 to July 31. If you have sales from last month they're not counting those. They started counting again on July 1st.