Hours Between Formula Not Working

So I have 4 hours columns. This is to track the time when you arrive at the mine, the time you go down, the time you resurface and the time you leave.

I can accurately get the time either in the mine or the total time.

(HOURS_DIFF({Mine Timeout}, {Mine TimeIn}))
(HOURS_DIFF({Surface TimeOut}, {Surface TimeIn}))

And it give me hours and mins. But if I try to subtract the MINE time form the total it always rounds to an integer. How can I get hours and mins in this last column?