d20 Chainmail weapon vs. armor

Below I've excerpted a few of the weapons and armor on the Man to Man (i.e. weapon vs. armor) chart from Chainmail. I converted the 2d6 target numbers to percentages, then rounded them to the nearest 5% to make d20 targets. The results were nowhere near what I expected.

. Weapon No Armor Leather/ Padded Shield Only Leather & Shield Chain Chain & Shield . 1 Dagger 6+ 8+ 12+ 12+ 14+ 18+ . 1 Hand Axe 8+ 8+ 12+ 14+ 18+ 18+ . 3 Mace 12+ 12+ 12+ 14+ 12+ 12+ . 4 Sword 8+ 12+ 12+ 14+ 12+ 14+ . 4 Battle Axe 12+ 12+ 12+ 12+ 8+ 8+ . 8 Spear 12+ 12+ 14+ 14+ 18+ 18+ . 11 Mtd. Lance 4+ 4+ 4+ 4+ 6+ 8+

I hope the formatting works out. I did the chart in google docs then exported to HTML, because I have no idea how to do a simple printscreen on my wife's Mac. Anyway, if you want to check my math or finish the chart here's the original:

Why no entry for a simple club or quarterstaff?