I believe "Current hit point total" means a character's number of hit points at full health.
Basically when temp hit points go away, if you are still above your max hit points, then you lose any extra above your max. If you are already below your max hit points when your temp hit points wear off then there is no change to your hit point total.
The word "Current" probably isn't the best choice, but the rule is pretty standard d20 stuff.