Fair Share distribution ATP qty to the sales orders via APO BOP variant

Hi Experts,

I want to distribute the ATP qty to the sales orders via APO BOP job in the below scenario Instead of allocating the total available ATP qty to the priority order/customer.

Stock 100,

Order 1 - 900

Order2 - 1000

then confirmed Qty should be 90 for Order 1, 10 for Order 2.

How can we set up this scenario via BOP variant instead of allocating the total ATP qty to priority customer/order.

In interactive BOP it is possible but How can we set up this in BOP variant job?

Thanks,