Update on surprise vacation pay

Alright, the answers were given to me in small blocks at a time, as I think we both were confusing. But here are the facts as HR presents them:

1) I do have vacation hours, and 30 were applied to my previous check.
2) I have been accruing vacation over time, but at "rates that vary per number of hours worked". Whatever that meant. But it is influenced by how much I work, which isn't a lot.
3) I have not lost any due vacation because the system carries over all vacation from year to year to year,  according to HR. I believe that is not the case, but I don't have the handbook with me to check. I'll do that next time I swing by.
4) I started accruing vacation in 2009, which is as far as the online system goes.
5) For the past 4 years, I've only accrued 80 hours of vacation, in bits and pieces at a time. That's about 20hrs each year.

I guess the good news is: I get to keep the vacation pay I received and the additional unused 50hrs. I was half expecting HR to retract on the whole issue and say I did not have vacation and my manager was wrong. I also have not lost any vacation, apparently, which is good. I will (eventually) try to figure out what the accrual rates are, an whether or not I have actually not lost any vacation. But that's a battle for another day.

Back to studying. 5 days to go.