Choosing this option allows reusing the disk hosting the ISO image. If you don't do it, the disk will be actively used to access the ISO image and it can't be partitioned by the installer.
Afran n textiṛit-a ad ak·akem-yeǧǧ ad talseḍ aseqdec n uḍebsi n tnezduɣt n tugna ISO. Ma yella ur tgiḍ ara aya, aḍebsi ad yettuseqdec s wudem urmid i wawwaḍ ɣer tugna ISO yerna ur yettizmir ara usebdad ad t-yebḍu.