that my friends is something i cannot answer since cipsoft itself didnt say how exactly that was calculated they only said it was 40% of your magic level and 30% of your level that is why i clarify that in my own experience is something close to a third of your full mana pool
If this information gets to me i will gladly change it but so far i think cipsoft or anyone else have said how it works
An example would be if 40%+30%= X and being X in my case is around 7000 Mana Shield Points then its 40%+30%= 7000 now im not good at math so i dont know how to turn those % to an actual number or logic of any kind