Hi out there

My freind is running in freetime and use a computer (GPS)
to track speed, distance and so on

Now the problem is
when i put this data in excel it's output is difrent ! why ?

eks.(GPS)
Distance 17,820 (17 km 820 m)
Time 01:29:05 (1 hower 29 min and 5 second)
Result= 00:04:49 min/km

eks.(Excel)
A1=17,820
A2=01:29:05
A3=A2/A1 Result= 00:05:00 ! why not 00:04:59 ?

What result is right Excel's or GPS ?

thanks in advance