Hi tkzv,
"Crossing Midnight" is a common problem in Numbers. It is a result of the Numbers Date & Time format. As Badunit explained, when you enter a Time, it automatically carries a Date (an instant in time since midnight at the start of 1 January in the year 1904).
Formula in D3
=IF(DUR2HOURS(C3−B3)>0,C3−B3,C3−B3+"1d")
Add "1d" (one day) to compensate 😉.
This may not work if more than one day is between Start and Finish.
That is how Date & Time works in Numbers. An instant in time since midnight at the start of 1 January in the year 1904 makes sense to me. 1904 was the first Leap Year in the 20th Century, and that makes it easy to calculate other Leap Years.
Regards,
Ian.