Minecraft Junkie

The repair skill arcane forging isn't set consistent (it's the default config as best I can tell)
Keep_Enchants_Chance:
Rank_1: 10.0
Rank_2: 20.0
Rank_3: 30.0
Rank_4: 40.0
Rank_5: 50.0
Rank_6: 50.0
Rank_7: 60.0
Rank_8: 60.0
Downgrades_Enabled: true
Downgrades_Chance:
Rank_1: 75.0
Rank_2: 50.0
Rank_3: 40.0
Rank_4: 30.0
Rank_5: 25.0
Rank_6: 20.0
Rank_7: 15.0
Rank_8: 10.0

This means at rank 7 you have 60% chance to keep all enchants, and a 15% chance to lose levels, so 25% overall to lose all enchants.

At rank 8 you have 60% chance to keep all enchants, and a 10% to lose levels, so a 30% overall chance to lose all enchants. That doesn't seem consistent.

Nevermind, I figured it out (thanks to #mcmmo)
<TfT_02> Look, here's how it works:
<TfT_02> for each enchantment, mcmmo calculates if you're able to keep it (the 60% chance)
<TfT_02> if the player is allowed to keep the particular enchantment, there is a chance that it will be downgraded (the 25% chance)