Checking Rule Error in MD04

Hello Experts,

We have been working on analyzing "Material Shortage error" in production orders.

Checking rule maintained in OPJK is PP with required parameters selected.

When I go to MD04 -->Environment--> ATP Quantities, I see the checking rule as BO instead of PP.

My question if instead of BO shouldn't we see PP and is BO checking rule being considered for ATP?

Thanks,

Parth