Game Mechanics: Shaman Canna

[Furniture]

I think it has something to do with the timing of the server tics and when you cast the spell, sometimes waiting a little after the server tic your mana will get subtracted by 1, once you see your mana go down by one mana cast canni and you will get the full canni, sometimes if you cast like right after the tic too quick you wont get the full mana, i havent really tested this but its just what i recall, i will test it next time im playing