Rookie KO

Thank you to the readers who responded to Renzy's count with advice about Rookie K.O.
A Question to the more knowledgable
Rookie IC starts at -20 when your RC reaches -4 you have an edge. Would it not be simpler to add 20 to both sums to get IC 0 and RC advantage at 16 ?
Or to save traversing zero, which can be confusing what about IC 20 and advantage at 36..... or am I missing something ????