When did you take your time last year?
This is kind of hard to explain. FMLA runs on a rolling 12 month calendar. So based on that, you probably have the 36 hours available as of now. That said, as 12 months passes from each day of use, you will gain that time back. So if your doctor put you needed to be on the leave for a year, at the end of the full year you would have gained back all the time from last year. Then they subtract how much time they think you could be taking (based on the doctor's note).
Since it is so person dependent, you need to call Leave & Disability to clarify what exactly is going to be covered.
