I have upped Heavenly Garb to exceptional version (mage plate base).
Previouly it was required 29 level, after up - 34.
I wonder, how does it calculate?
Is there some formula?

I guess it must be level 29,according to base (mage plate) level required, but it is higher
Why?

normal to excep: +5
excep to elite: +7
double upgrade (normal to elite): +12 (5 and 7, cumulative)

Thank you!