They are not B Frame, they are A Frame. I did the test with a screenshot now as far as it would go, cause the duration is low.

http://prntscr.com/kqcmuw

Order of (de)buffs: her atk buff, Tsuku Light Res down, her atk down, her def down, Outrage atk and def down

Diana also was never able to overright it, so it is 16% or more (since I've never seen that I guess atleast 20%).

(No bully for correcting please >_<)