Each anti-tank weapon fires at least one type of ordnance. Each armor rating that the round can penetrate will either have a base To Kill chance (TK#) stated as a number (non-kinetic rounds and large over-matches), or a base penetration distance. The latter is to simulate the reduced effectiveness of kinetic rounds over range.
There are four possible TK# numbers when a round has a base penetration range:
A 20mm Anti-Tank Rifle (such as the Finnish Lahti ATR) penetrates I armor at a base of 12" (600m), and II armor base 0"
37mm L/45 weapons like the PAK 36 or wz.36 penetrate I armor at a base of 24" (1200m), and II armor base 16" (800m)