Lets say that you get hired Nov 10, 2016.

When you get out of IOE, you will be able to bid for vacations. You will get to bid for 2 weeks in 2017, since your anniversary date falls in 2017. If you want to take both in July or August (and they are available) you can.

If you quit before your anniversary date of Nov 10, 2017, then you will have to pay back the one extra week of vacation that you took and had not earned to that point. But, if you stay employed or leave after Nov 10th, then you don't.