say i have +min or +max dmg on shield or hat , how does that effect dmg from grief?

🤔

min/max damage from all sources is factored into total dmg in the same way:
https://www.theamazonbasin.com/wiki/index.php/Damage

it does not affect the dmg of grief (i.e. your weapon), but the total dmg. not quite sure what your question is

say i have +28 min dmg on my helm. wondering if it just adds to the base dmg from wep shown on c screen, or adds to the +400 hidden dmg.

the implication being it would be really goood if it added to the +400 before the ed% multiplier. but really ineffective if it just added to the base dmg of the wep shown on c screen.

the link i gave above provides the algorithm and thus the order in which all contributions are considered. do yourself a favor and ignore the character screen^^