Principal dx = M12.812Original procedure performed and principal procedure = removal of humeral head device from a hemi shoulder 0RPK0JZ, replacement with humeral and glenoid components for a reverse shoulder 0RRK00Z, DRG 483, RW 2.3835.Additional procedure performed later during the stay = excision of a lesion in the subQ of the right thigh 0JBL0ZZ, which changed the DRG to 465, RW 1.8374.I ran this through our standalone encoder as well as 3M, with the same result.This doesn't make sense to me. Why would the addition of the lesion excision procedure change the DRG from 483 (which has a higher RW) to 465 (which has a lower RW)? If anything, I would expect the DRG to remain the same or possibly cause an increased RW, but not reduce it.Am I missing something obvious? Am I using 3M wrong? Is there some rule about the EXCISION root operation that everyone but myself is aware of?