ToME: the Tales of Maj'Eyal

It says that you can only apply one per target per turn and that the jinx lasts for 5 turns. Then, the other skills in the category require at least 6 stacks... but how is that possible? I don't understand.

Based on pure guesswork and having played the class like once a year ago, I'd say that applying a new stack of the debuff refreshes the duration and that stacks fall off all together, not individually.

Thank you!