Word of Healing Broken?

ok so it's my understanding that with this elite monk spell, if the target is below 50% health they get healed for 100 additional points.

Well, I'm pretty positive I can tell when their bar is below 50% but for some reason it still only shows +80 above their name. Only a few times have I seen it say +180.

Am I misinterpreting the spell description?

maybe the health bars arent as accurate as they should be

That was my first thought, but I've used it many times when they have 25% of health or even just a sliver of health, but still no +180.

dont know what to say

I also have a few characters with WoH

sometimes I miss the mark for when I think they are 50% health
but I've *always* seen the spell work correctly if players below 30%