question on combat

[Jian]

I find it quite odd that whenever a cruiser (6/6), or any other combat naval unit -other than frigate/sub- for that matter, makes an attack on another similar unit, the attacker nearly always wins. I have read somewhere that the calculations are based on a random number - in this case it would be 120 60+60, thus the chance of attacker or defender winning should be the exact same. However, through experience it seems that the attacker more likely wins if they start off with equal hp.

Could anyone explain this for me please?