I was messing around with /entitydata and made a XPOrb have negative a value

What I expected to happen was it to take away xp

When I picked it up it only removed the xp on the bar not the level and I can no longer gain xp.

Steps to Reproduce:
1. /summon XPOrb ~10 ~ ~

(use /entitydata @e[type=XPOrb] {} to check)
2. pick it up
3. Notice that it only removes xp on the bar
4. splash some xp bottles on you
5. Notice that when you pick them up they give no xp (same thing with /xp)