The ICB reviews the PoE annually and the academic board then decides on the mark composition based on various factors.
If a PoE is worth 30% and let's say for example Test 1 is worth 3% of the 30% and test 1 itself is worth 100 and you received 73 out of that 100, your mark will be calculated as below
73/100 x 3 =2.19
This means that you have achieved 2.19% out of 3%