For everyone that has had identical time for DPS, you are only getting credited with withdrawal time.
You are not getting any credit for days with less than 400 DPS letters and days with multiple runs of DPS.
You are supposed to get a casing credit for those days mentioned. It is a decent per piece credit. As such, for your numbers to be IDENTICAL, there is no way you got credit for any of those days with the DPS exceptions.
This is nothing new. The USPS has known about it since the first survey and has refused to pay. I've filed a dispute every time and it's never been resolved.