Ok, I'm officially an idiot. You're all correct of course. It's rounding the integer and not the decimal.
The progression on the greenest mobs I could find is like this:
24.42
25.44-25.52
27.53-27.74
28.74-29.94
30.94-30.04
31.04-
Strange rounding they are doing. That jump from 25.-27. is not a typo btw.
I hope you got some good entertainment value out of this at least.
Sorry for the confusion.