The way I think of vacation and reserve is this:
You can’t have a day off you would have had on your schedule anyway count as a vacation day.
So even if all 7 of your Vaca days fell on days off, you would still have 7 R-days removed from your schedule. Sliding or bidding a reserve schedule that conflicts with all or some of your vaca days just gives you control over what days are actually remove. Otherwise, that is up to scheduling. You can enter an input but it’s just a request. They have the ultimate decision.

Extending vacation is just a math problem resulting from the fact that a vacation day is worth 6CH and an r-day is usually 4.5-ish CH. It is done by using the actual vacation hours your Vaca is worth divided by r-day value to determine how many extra r-days you can knock out. Contract is pretty clear on now to calculate that.

Make your choice via vips during the conflict window between this afternoon and Saturday morning. Any days removed via extension are also just a request from you. Days will get removed according to the formula but may not be the ones you want removed.