The total supply of items is defined by its rarity - the rarer, the less of it there will ever be. Starting from the 1st Generation of Polygon NFTS, these are the items sorted by rarity:

Common - Normal virtual items with an unlimited supply. Not FTs/NFTs.

Uncommon - FT items with a limit of 10,000-20,000 items minted

Rare - NFTs with a limit of 500 items minted.

Epic - NFTs with a limit of 200 items minted.

Legendary - NFTs with a limit of 50 items minted.

Mystic - NFTs with a limit of 10 items minted.