Well, Claudio, I don’t think you should apologies for your questions: asking for help is NOT shameful.
Personally I’ve seen a lot of Natural code where N format is used for tax calculations - not the very efficient way to do it at all. By the way, all of those I1, I2, I4, P and N may be negative - just as in COBOL I assume; example: -128 <= I1 <= 127; -32768 <= I2 <= 32767 and so on.
As for “…in cobol to me seems more straightforward this” I’d say “everything is relative, and only Sweden vodka is Absolut”