On my 941 report how do I reconcile differences in the SS tax between calculated and actual amounts?

Hi,

On report R078500 941 Worksheet I have a difference in my SS tax amount between the calculated total and the actual amounts withheld from history total. I cannot figure out the difference and I would like to reconcile the amounts. How can I find my difference? Is there a report I can run to see how it is calculated and then compare to each employee's tax history?

Thank you!