Cumulonimbus Stats Change?

So I’m 1.20.3 cumulonimbus was nerfed from 40% to 33% spell dmg.
I right before the nerf bought a 100% one with 40 spell dmg percent
But after the nerf it wasn’t perfect, as it’s currently 32 and not 33
It’s not that big of a deal for my dmg, but kinda annoying for selling it as if I wanna sell it later being perfect makes the price go up a lot, so I basically just wasted emeralds buying it :p
So basically I’m just curious why that happened

 

rounding

each stat has an internal roll from .3 to 1.3 (.7 to 1.3 for negative stats). the actual value of a stat is its internal roll multiplied by the base value of the item's id. when the base value changes, that internal roll might not be high enough to round to the max possible roll anymore