 # Calculating Annual leave

I am trying to set up a simple formula so that I can track the amount of  leave hours I've accumulated each month.

I have a spreadsheet that tracks my work activities (that someone else created).  Each month is a different tab and I already track how many hours of leave I use each month. The total leave used for the month is  cell C50 and is formatted using the custom number formatting of [H]:mm;@ so that it will display like this 15:30 (15 hours and 30 minutes used in January) .  If I know I'm starting with 100 hours and I will add 14 hours every month how do I set up my formula?

It seems easy enough Starting in January in  I have 100+14-the value in cell C50 then in Feb I should just take the value from January's leave balance + 14 - the value in the cell C50 and so on.  But I can't figure out how to get this to work.  I suspect you have to do something specific because I'm working with time values  as my formula =(100+14)-C50 gives me a result of 2720:30 which makes no sense to me as the end result should be 98 hours and 30 minutes.

``=(100+14)/24-C50``