Not sure how that number's coming up.
Seems more like this would be the case:
A character that's added to the list after reaching level 25 but hasn't been tracked with Glycerine or HeroStats would essentially show up as having zero experience out of the 360,919 accumulated XP to reach level 25 and 446,119 accumulated XP needed to reach level 26. Going from 25 to 26 requires an increment of 85,200 XP, so that would be like saying since you made it to level 25, you've somehow accumulated -360,919/85,200 XP. That should come out to about -4.236 or -423.6%. That's nowhere near the number it was showing for your character.
Odd.