Why delivery is creating with ZERO quantity for STO?

Hi,

We are creating delivery through VL10G for STO , and delivery is created with zero quantity, however there is stock for the same article and supplying site, which we can view in MD04,

We know, how to stop to make zero quantity by making changes in delivery related item category for transaction code 0VLP, but we would like to know that why it is creating with zero quantity, even though there is stock,

Our ATP check is defined in below manner,

In STO, we can see that the define checking rule is

Availability check: 02: Individual requirement

Checking Rule: 01 - Checkig rule 01, Attached screen shots as well

Also we have defined the assign delivery type and checking rule  01, Attached screen shots

Please advise, why delivery is creating with zero quantity for STO (UB purchase order type)?

Regards

Vanraj