Ah, forgot that Kyotomi copied her data to this thread. Copying my reference post here.

Fractional factor:
The percent increase is almost certainly in units of /256 (but maybe /128) based on other info. So +20% is 51/256 (0.19921875) and +30% is 76/256 (0.296875).

401 * (1 + 51/256) = 480.88671875 => 480 (match)
401 * (1 + 76/256) = 520.046875 => 520 (match)

And yes, it's additive with Defender:
401 * (1 + (64+51)/256) = 581.13671875 => 581 (match)
401 * (1 + (64+76)/256) = 620.296875 => 620 (match)