Hello
These settings from transaction OMPH are only considered when PIRs are created from a reference, such as APO, SOP or forecast, however, this setting is not considered when creating PIRs directly on MD62.
The distribution function is used if you want to distribute a different percentage for each period (e.g 40% in the first week and the 20% in the subsequent weeks). I have never explored such functionality and cannot provide more details.
BR
Caetano