How does armor work?

[LCCX]

I just started New Hope mission 4 (escape on the airplane) and realized that there are *2* heavy armor items in my character's armor slot. I checked out the big worms to the south and they *murdered* me. I don't understand at all how the combat damage system works. In theory, there is some good information on the wiki:

• The player character has 50 base health: https://wiki.factorio.com/index.php?title=Lua/Player
• Big worms do 60 damage per hit: https://wiki.factorio.com/index.php?title=Worms
• Armor has a 2-part resistance system and a relatively very large pool of durability: https://wiki.factorio.com/index.php?title=Armor
• Armor's first resistance part subtract's damage: https://wiki.factorio.com/index.php?title=Damage
• I presume that the second armor resistance part reduces incoming damage by that percentage since higher/better armors have a higher percentage resistance.

Therefore, in theory, a big worm would deal ((60-5)*(1.0-30%)) = 55*0.7 = 38.5 damage per hit to a character wearing heavy armor. But that doesn't quite seem to be the case... If that damage were applied to the character and the prevented damage applied to the armor's durability, then a character should die in 2 hits. If the worm had to eat through the 5000 durability before wounding the character, then a character should die in 84 hits. But I die in 3 hits, taking 34-40% damage each time, watching the green health bar.

I have tested and established that stacking additional armors only add to the stack's total durability.

So what is the math that results in a character, wearing heavy armor, dying in 3 hits from big worms, taking 34%-40% damage each hit?

[orzelek]

Three differences I think:
1. First use %-age resistance then substract the absolute one. In this case result is quite close.
2. Armor durability has nothing to do with damage absorbtion - it only shows how it wears out from using.
3. Player has 100 health.

[LCCX]

Excellent, that's it. Thanks!