I think i'm getting where the 6% comes in. going by what you said, say the original damage is as follows:

5000 base, atk buffs add 20% (so 1.2), damage buff is 2.2 cause a skill went off, and it did a critical so 1.5

that's the following:

5000 * 1.2 * 2.2 * 1.5 this equals 19,800

but if that crit damage increase is +10%, then it's this:

5000 * 1.2 * 2.2 * 1.6... this is 21,120

unless my math or something is off, the end results would be 19,800 without crit damage, and 21,120 with it.

21,120/19,800 = 1.066666.... which honestly would round up to 6.7% or 7% with a flat number. that sounds about right.

but i'm not sure why 1-turn is in it's own thing. i might not have noticed anything when i used it cause i thought it was 10% atk just added to the total for a turn (still put it on whaleship though due to trying to deal a lot of damage to the crystal in case a non-crit team appears)