you did not get me. I said the unpartitioned space could be use to alternative OS or as another partition.
If you don't want another OS there, format it to use with your existing OS. For novice users just forget it. 100GB is not much lost if you have 1TB For people that like to install other OS win.. requires at least 25GB I guess.
Leave 50GB unpartitioned then. Whatever.
I don't see the point only leaving 5GB, cause that would only suit AROS then. Nothing else.