An enchantment table has three options to enchant an item, each with varying level requirements. For example, I am going to enchant my diamond sword with 30 enchantment levels.

I need at least 30 levels to get the enchantment. But when I buy the enchantment, it only takes 3 levels away from me. It should take 30 but it only takes 3.

I still need the 30 levels to get the enchantment or it won't work. The amount it takes is dependent on which square take it from. If I get a top square enchantment it will take 1 level, middle square will take 2 levels and bottom square will take 3 levels.

Make sure to have the enchantment table take 30 levels, not just 3.