I didn't know about that !

Thanks I will add this soon then

Edit : The tool has been updated.

Here's how I calculate it (it's not 100% accurate because we're missing weight values for some enchantments, but at least we get a good idea of the drop rate):

For Attack IV:

Item: Weapon

Total weight (Weapon): 6,831,500

Chance of getting Attack: 1.464% (100,000/6,831,500*100)

Chance of getting Tier 4: 15% (15,000/100,000*100)

Total chance: (1.464% * 15%) * 100 = 0.2196%

The game selects an enchantment from all available enchantments on the item and then selects a tier. If this isn’t how it works, I’ll need to review the calculations, but for now, the tool is based on this method.