I’ll just pop in here real fast. Low luck dice works like so: Add up the to-hit number of all the units in each attack column separately and divide by 6. So say you are attacking with 6 infantry 3 tanks and 3 fighters.
So the infantry attack on a 1. You have 6 so 1x6=6 Now divide this number by 6(the number if sides on the dice) and you get 1. So that is one guaranteed hit. Next add up the tanks and the fighters since they all attack on 3 you group them up. 3x6=18 18/6=3 So 3 guaranteed hits. I just grabbed these number out of the air so lets say you are defending with 8 infantry and 2 fighters. Infantry defend on 2 fighters defend on 4. so 2x8=16 16 divided by 6 = 2 guaranteed hits with a remainder of 4. Since you can’t divide 3 hits into it fully. That 4 remainder now acts as a normal dice roll. You have to roll a 4 or less for a hit. The 2 fighters now 2x4=8 So that’s 8/6 =1 with a remainder of 2. So 1 guarantee hit and now you must roll a dice with a to-hit on a 2 or less.
Hope this helps.