Rebates not getting calculated correctly

Hi,

I did a basic set up for rebates for Sales Order through advance pricing.

I set up rebate as below

For 1 qty= 10% rebate

For 2 qty= 20% rebate.

When i created the order with 2 qty, the same got reflected correctly at the line level in price history.(20%)

I also did the sale update for the SO and DMAAI 4270 and 4280 got correctly hit.

Also the rebate value was seen in F4079/78

However when i created a new SO with 1 qty, then ideally 20% rebate should be seen, because i have crossed the 2 qty mark in the previous SO.

But i could see only 10% rebate applied, which is incorrect.