Did i do something wrong or did i find a bug ?

So context, im making a shield getting lucky with random mods i guess,
i used a few exalts to get this shield to this:

*lvl 50 tower shield 71 str*
*+142 to armour*
*71% increased armour*
*+21 to strength*
*+7% fire res*
*+18% cold res*
*+11% stun thres*

Now here is the thing, it showed around 500 armour so i upped it to +20% quality plus added an iron rune (+16%) to get it at around 600 ish.

Then i rune warded it and went to equip it.

It now shows 312 armour !???! shit feels like i won while rolling and then still lost..

Please someone explain to me what i either did wrong or if it is the games fault.

https://poe2db.tw/us/Intricate_Crest_Shield
https://poe2db.tw/us/Runeforged_Intricate_Crest_Shield
https://poe2db.tw/us/Runemastered_Intricate_Crest_Shield

It doesn't seem like Runic Ward is a "free" stat to add.

Thanks for your reply.

But i have no idea where to look at on those links, still learning this stuff.

The shield is rune-forged. thats all i could tell you.

What on those pages would give me more information about what happend to my shield ?

All gear above item level 55 (not level required to equip) sacrifice some base stats in exchange for ward when rune forged.

Don't you love the new amazing league mechanic that is totally not broken?
What you did wrong is putting your item onto the verisium anvil. Never approach that sht. It takes away from core defences and turns that into ward resource. Randomly.

Thank you all for the info, good to know where i fucked up.

Sucks at a shield warr tho.... that 600armour looked so juicy