Iron Warriors bug?

[Viajero]

I see. Thanks. Everyday one learns something new indeed.

But not sure yet how things stack never really understood it so better ask now that is relevant! , i.e.:

Tartarian´s base protection = 4
Displacement armor = (Protection, Body)18
Black Steel Helmet = (Protection, Head) 23
Shield of Gleaming Gold = (Protection, Shield) 22

Result, Total Protection: 21
Total protection head: 25
Total protection body:20

After "Iron Warriors":

Result, Total Protection: 30
Total protection head: 32
Total protection body: 29

??????

- Is the shield factored in here somewhere? How?
- Is the way things are stacked by using half the base protection and then adding any armor/helmet on top? still, this does not explain what happens after Iron Warriors...
- Hows the overall Total Preotection Figure calculated?