Abou damage plus status

Damage plus adds flat damage, like the divinity ability. It functions as the opposite to damage cut.

It adds flat damage per command card.

Like, say, a +800 Damage Plus will add a total of 3200 damage if the Servant uses a Brave Chain (3 cards plus the Extra card). Even if the attack has 5 hits, the 800 damage will be divided so that it still totals up to 800 at the end.

It's more useful for normal attacks since NP damage is generally in the range of tens of thousands.

It's very useful in cases like Siegfried during the previous Nero Fest, where his defense buff was so high that normal attacks did pretty much nothing to him unless it was buffed by a massive amount. In this case, Damage Plus pretty much ignores the added defense.

It is a kind of plat damage increase. You can consider like some extreme cases, your servants can still deal some damage to a enemy with 100% defense-up, because of that damage-plus.
It is not quite versatile as attack-up, but very useful in such circumstances (meeting enemies with huge defense-up buffs, or class disadvantage).