Field help (PTOSHTFCT) 

This factor is a number of days to be applied so as to sort the requirements to be assigned. The factor is calculated as follows:

1 * Priority factor = shift day number

For instance:

Priority factor 10
SOF number 1 for the 06/25
SOF number 2 for the 06/30, shortage quantity present

Here, the request to be assigned in priority is the SOF number 2 since its fictive requirement date changes to 06/30 - 10 = 06/20 due to the shortage quantity.