Update during update

I finally persuaded my friend azeem to buy halo 5 a few days go. His game had updated 80 % when the ghost of meridian went live. He says if he has to start over he’s returning the game which is unreasonable but anyway, whats gonna happen

Well I mean depending on how xbox does their updates he might have already had the data sent to him preinstalled so it would have jumped back to 80%ish pretty quickly if not then he would have had more data sent to him during his initial download which would mess up that download forcing him to re-receive all the data sent again