Subtracting Time (splits)

I am a race director putting on a triathlon and we are using stopwatches for a kids triathlon. I would like to enter the data into excel, but am struggling to format certain cells to subtract one time from the other. I will give an example of what I have.

C3 (Swim Time) D3 (Transition Exit) E3 (T1 Time) F3 (Bike Enter) G3 etc...
4:06 5:40 1:34 22:00

E3 should be the subtracted time of Swim Time & Transition exit... One of the problems I am having is not knowing which "Category" to select under format... because everything I tried converted it to AM/PM h:mm:ss... I think for this race I will only need mm:ss (the race will be under 1hr). I have tried for E3, doing =d3-c3 but that doesn't do it.

Any help is greatly appreciated. My race is in two days.

Thanks again!