It says
+40% damage per Status affecting target
but tested with lv80 heavy gunner with only serration(165% damage) equipped, it deals 105 damage with no status, 113 with one, 121 with two and so on (critical headshot).
For the incarnon mode, the damage is 127, 140, 151.
Apparently the bonus of Fatal Affliction does not stack multiplicatively after the base damage mod, and since Galvanized Aptitude ignores the innate damage of the perks, we may expect Fatal Affliction is the same case.
But [12*(1.65+0.4)+12*1.65]/(24*1.65)~112%, and 113/105~107.6%, 140/127~110%. Still it's lower than expected.