well [time in seconds] * 60 it not accurate. it should be time in seconds / 60 and event there the decimal is not correct as the report will show time as 1mn 75 seconds and not convert the time after the decimal in minutes.
It would be nice if we could have a better view on this in HH:MM:SS
even in the calculated metrics turning the value in time rounds up or down to minute.
and there can be a huge difference when the time is rounded iup
1m01s is rounded to 1mn
1m31s is rounded to 2mn
for sites with few seconds spent on site it is a huge difference.