Very confused...Primeval Stone glitch?

Ois - Lost City

I recently started sharding some of my gear with vitality stones and was keeping track of what my defenses were increasing to with each vitality stone.

In my Lunar Mantle Radiance cape I added one Primeval Stone. This increased my base unbuffed defense by about 50-80 points to 7152. On my second Primeval Stone my unbuffed defense increased by 2 points to 7154.

I checked my stats before I imbued the second shard and the only thing that changed was the addition of one vitality stone.

So then out of curiousity I unequipped my weapon which has 19 vitality 1 crit and -int...and my defense went from 7154 to 7092.

The only thing I can think of that might affect the results is if vitality gets multiplied in sets of 20...like dex does for crit.

How the hell does this multiplier work for vitality... -_-


*Edit: I might also add with the second vitality stone my magic defenses went from 4155 to 4157 unbuffed.