sorry to hear that let me see if i can explain it better, the resulting mana shield is based on 40% of your magic level and 30% of your level it doesnt protect your level or ml when you die, tibia in the test basically told that but didnt explain very well on how it was calculated, on my own experience the resulting mana shiled is something close to a third of your full mana only and if you want to refill that mana shield need to use a mana shield potion
just added a clarification hope this will help other to understand what i tried to say
If anything else is hard to understand just say it and i will try to explain it better, thanks for the suggestion