here's how it works:

if you take a break during regular fall or winter semesters (approx 18 credits per sem max for most colleges) then obviously, you need to repay for the lost credits. so it is the 18 hrs you need to payback, not 24 (at least this is what happens in my univ).

so, if you take a leave in the fall, then you'll have to either take more credits in winter and spring  OR take both spring and summer to repay the missed credits and then do fall and winter next year as your regular semesters. personally, i'd go with the second option, ie, fall (leave) - winter - spring - summer - fall - winter.

btw, some colleges don't have both spring and summer terms. in mine, we call may-june spring term and july-aug summer term and you can take upto 9 credits each term (thus, total 18 credits = filling in for the lost sem).

hope this helps!
and recover soon.