I only have one account buddy, glad it's not just me...
Have just asked in faction chat if they all thought a unit boost would add that boost to all active army units of that type, working the same as a boost building offering the same bonus type (+30% to sea defence).
Therefore how could two buildings at lvl 15 offering 150% (75% x 2) add 3bb to an original figure of 500aa
I am going to have a quick look for reference the total amount of sea defence from units in my army from the start...