possible reason for a Location having negative quantity

Hi All,

I am running a Pick Request program R46171 and one of the locations quantity became negative after this program completed.

There are two locations:

Location         Quantity

Pick01                9 CT

Pick02               40 CT

The order was created for Quantity 50 CT.

After the pick request was executed, the location availability is as follows:

Location         Quantity

Pick01                -6  CT

Pick02                 5   CT

Attaching the item availability screen before and after the pick request program and also the pick request program screenshot.

What could be possible reasons for the location pick01 go into negative?