Why are there multiple Calculate Payroll process lines showing for same month in Balance Results?

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I'm looking for a bit of help understanding something that we're seeing in Balance Results screen. When I go into Person Results for an employee, and then into Balance Results beside the Calculate Payroll flow for a previous month, in the dropdown menu at the top of the screen I can see 2 or 3 lines that all say 'Calculate Payroll' for the same month. All but one have a Retro ID so I'm guessing it's something that's created by the Retro process. However, when I look at one of our balances, 'Holiday Pay 12 month Average', the balance value