How does Service Contracts Main Billing Program calculate invoice amount based on price breaks for u

Question: How does Service Contracts Main Billing Program calculate invoice amount based on price breaks for usage?

Problem : I have created a contract and a usage item line. I have tagged price breaks of 0 amount to be charged for count 0-1000 and 7 to be charged for usage between 1000 and 9999. I have locked the price break for the usage.

I then set initial counter reading as 0 and then entered  a counter reading of 7000 so that the net reading is 7000.

But when i ran Service contracts main billing program it calculates amount as 6.3 for the counter reading of 7000. As per my understanding since the counter reading is 7000 and falls between 1000 and 9999 price break it should calculate 7, but its not.