You get to request which days you want to stand reserve,
if I understand the math the company gave you, 8 days + 5 day extension means 13 R days are going to be gone.

Doesn't matter whether any of them actually are in the footprint of your vacation. The slide and the buffer will prevent CRS from putting any remaining R days on those particular days.

bid period processing has a place where you can submit you're I'd like to do my remaining R days on these calendar dates.....kind of like a VTO line. Except, I've had better luck with the vacation reserve line rebuild versus VTO