Its random, and each potion has a range of possibilities:
There is an equal chance of you regenerating any number that is inside this range, for an example: the chance of regenerating either 75, 76, 77, 78... 125 mana when using a Mana Potion is 1/51 (~2%), because there are 51 possibilities in that range. Your magic level and level does not affect the possibility of an individual number to get chosen, its all random.
The ranges above were taken from: https://tibia.fandom.com/
It depends randomly, for each mixture is assigned a value whatever it can give maximum.
statics based on Tibiopedia.pl
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