I really think it's an error to divide by 60 in column I.
how I see it:
Column i counts the seconds of all needed rows from column f (let's say no division by 60)
Column h = count of minutes from column e + seconds/60 to convert seconds into minutes decimal
Column g = count of hours from column d + minutes/60 to convert in hours decimal
If you divide by 60 in column i, and you divide this once again in column g in the formula
SUM(E2:E4)+I2/60
You'll have a division by 3600.
That's how I see it.