What do the numbers actually mean???

[Cornfed77]

I've had battleships and battlecruisers destroyed with one hit of 2 or 3k damage, ive also had an enemy ship turn its tail and run and put up its shield of invincibility.  Last night I had a custom battle were i did 10 on 10 battleships at 1k range.  Of course without being able to select a tonnage or minimum gun caliber to face I ended up with 10 80k ton 18in armed ships verse 10 41k ton  14in ships.  I killed 9 ships quickly, the last turned tail and ran, I had 10 battleships each with 12 18in guns shooting at it as it sped away, everything was red, all guns disabled, and the ship took well over 100k damage and hundreds of hits from both HE and AP.  The structure damage hardly moved and flooding never increased.   Finally after a full 10-15 min of shooting at it with 120 18in guns it sank.   Not sure what was intended with the Structure/flooding but it really appears broken.  Same with the difference in shell impacts on the side of the ship and torps.  I can get some big numbers for damage from side shell hits that do not cause flooding, but a torp hit for 7 damage will cause flooding almost every time.  I would love to know how the protection/armor system on these ships is supposed to work.