When nominal time and effective time diverges (I claim it’ll have a cooldown of 5, but truth is that it is never 5) it means someone does not know how to deal with FPS.
Usually things like cooldown are re-calculated every frame (instead of every second). The amount of frames per second is also not a fixed value, so it is really easy to include time bugs because that. (High-performance devices will present faster cooldowns, and low-performance devices will take longer to do it)
…Well, I never played Djinn Caster and have zero interest in downloading it, but usually what I said above is the cause of time inconsistencies.