[spoon]

What does this mean?

I thought stealth and scattering armor gave the ship a 15% defensive bonus, thus making it harder to hit. And once hit, a ships damage is calculated normally.

Where did 165 and 290 damage points come from? And what is the explanation for their use?

I believe it is wrong, and you can safely ignore it. The 15% is additive, so the benefit you get on it varies based on the probability of being hit. If we knew what the average chance to hit was in SE4, then you could apply a system like this to figure out how much damage the stealth armor saves you from.

Bottom line should be: put both armors on all your attack ships, with a few exceptions. For example: Ships designed solely for worm-hole defense might want to skip them in lieu of more weapons. Ships designed to fight a race with Talismans don't need them, either).