I keep statistics for and Ambulance service . We post departure and arrvl times and then the elapsed time enroute.
In excel, one could use the formula (=(a3-a1)) and get answer expressed in minutes provided the cells referenced in the formula were formatted as time (military). It was fairly automatic in Excel, but Numbers won't seem to do it at all. There are 25 different formulas listed for time expressions but none expresslyfor this.
Also, two other funtions we used a lot in Excel were "fill down" command to paste the same formula in an entire column or row with corresponding cell relationships retained down the column.
and: 'Freeze heading' to keep row and column titles visible while scrolling through a large worksheet and visually keep your place. Can't find thoset either, must be a particular search term for it in Apple speak?