Payroll STP verification report

Hi , i hope someone can help me with this one.

When i compare the STP2 Verification report to my accountright payroll summary report i have a difference.

The difference is for an amount of $390.39 which i can identify as a Back Pay paid to 1 employee.

This (Back Pay) is in the category for STP2 of Gross payments, why would it be missing off the STP2 Verification report.

I have checked and the Payroll report send to STP on the day was accepted.

This has me confused, does anyone have any ideas?