Tool durability bar is incorrect

So, in Survival, I have a Iron Sword at exactly half durability (175/250). However, the durability bar disagrees. It shows that the durability is more than half.

To reproduce:

1. Get an Iron Sword through any possible means with a durability of 175/250.
2. Observe the durability bar. =D

(As a side note, the world was created in 1.8.2-pre4.)