Reduced attribute req

Hi, maybe a dumb question but I just got a new two handed mace that I want to wield with my shield.

The weapon itself has 20% reduced attribute requirements on it with a total of 169str requirement.
With the node to allow me to wield 2handed and shield together I need x3 strenght req which is 507 strenght.

I´ve got 485 strenght on that weapon slot but still cannot equip the mace. The req should be 169str*3-20% which would be 405.6strenght, right? Still I cannot equip it,

In weapon slot 1 I got 507 strenght and there I can equip it.

IS this a bug or am I missing something?

lvl 88 warrior.

EDIT: It´s on PC, I missplaced the thread