Stacking Kinetic Buffs

Is this how its supposed to work? seems very broken.

Serrated munitions gives +30% kinetic and -20% HP. but the kinetic bonus seems to stack for the whole fleet of 6 ships. giving each ship +180%. if this is meant to be how it works why does the -20% HP not stack? These are custom designed ships with 1x Serrated Munitions each.

Each ship when not in a fleet does 108 dmg but when combined in the fleet of 6 does 140 each. Even more confusing is then  the fleet then says the total kinteic dmg is 1036. even though 140x6 is 840. Am i understanding this all wrong?

Thanks!