1440 = 24*60, i.e. the number of minutes in a day. Dates are stored as
numbers in Excel, Jan 1, 1900 being number 1 and increasing by one day
since. So VALUE(TODAY()) = 38839. Time is stored as fractional part. So
noon today is VALUE(TODAY()+0.5) = 38839.5.

By this token, if you enter your minutes as integers, they have to be
converted into the quantity that Excel thinks as a minute, which is
1/1440. Then you sum these quantities and you get a number probably
much smaller than 1. If you format this as time you will see it as
minutes.

Does this help?

Kostis