How is the depreciation apportionment percentage determined?

Depreciation rules were established for FY23 to accommodate new depreciation tax laws. It's been determined the apportionment percentage should have been 100% versus 50% for a particular user defined depreciation rule. In reviewing the depreciation rules and associated formula's, it's not clear how the apportionment percentage populated on R12855(Depreciation) is determined. Thanks in advance for your feedback.