Some people may use
Rafe as a nn for
Raphael... sometimes you just have to know which case it is for certain people... just like
Kate could be for
Kathryn or
Kathleen or
Katelynn or just
Kate or
Katie and you can't just assume which it is. The main difference is that those are at least related.
Jenny/Genny could just be
Jenny or could be
Jennifer or
Geneva or
Genevieve. Doesn't mean it's only valid for 1 of those even though they're totally different names.