Angle sum is the sum of all angles (exterior and interior) while interior angle sum is sum of all interior angles.
For example a square has an interior angle sum of 90° + 90° + 90° + 90° = 360° since all his interior angles measure 90° and there are only 4 of them.
It's total sum of angles is much bigger (interior + exterior angle sum)
The exterior angle sum of an square is 4 × (360 - 90°) = 1080° and you must add the interior angle sum which is 360° so we have 1080° + 360° = 1440° and that is the total angle sum.
As you can see the interior and total sum of angles are different in size and therefore are a different things.
Hope this helps.
r3t40