PresaleBenchmarkMap.md

mapping(address => uint256) amountLeftToMint;
addUserToPresale(address _buyer, uint256 _amt) external onlyOwner {
    amountLeftToMint[_buyer] = _amt;
}
function presaleSingle(bytes calldata _proof) external payable {
    // ... other require statements
    require(amountLeftToMint[msg.sender] > 0);

    amountLeftToMint[msg.sender]--;
    _mint(msg.sender, totalSupply());
}