Matrix Games Forums

I have been working through understanding the effects of terrain, weather, etc. on land combat outcomes. I think I understand the die roll modifiers: attacking units in a city (-1), snow weather (-4), the armor modifier (-1) is I believe for having a defending AT unit against Armor unit.
What I can't figure out is the Odds Ratio of 50:13? The attacker of value of 50 I can get but the defender value of 13 is the stumper, I get it to 10 which is garrison of 7 plus AT of 3. Where does the other 3 defense units come from? Any thoughts or insight?

Anti-Tank units have double factors when attacked by any enemy MECH, ARM, or HQ-A units. AT units with a red combat factor double their factors on the attack against enemy armor.

Anti-Aircraft units with a pink or red combat factor are also doubled this way.