Wanting to understand what these numbers mean

Smart Contracts
1

Can someone please let me know if these numbers are correct? I'm starting with 1 quadrillion tokens. I will have a 3% buyback fee, 3% marketing fee, 3% redistribution fee, and 1% dev fee. I can post the full code if that will help. Any help is greatly appreciated.

  uint256 private constant MAX = ~uint256(0);
    uint256 private _tTotal = 1000000000 * 10**6 * 10**9;
    uint256 private _rTotal = (MAX - (MAX % _tTotal));
    uint256 private _tFeeTotal;

  uint256 public _maxTxAmount = 1000000 * 10**6 * 10**9;
    uint256 private minimumTokensBeforeSwap = 200000 * 10**6 * 10**9; 
    uint256 private buyBackUpperLimit = 1 * 10**18;

   uint256 contractTokenBalance = balanceOf(address(this));
        bool overMinimumTokenBalance = contractTokenBalance >= minimumTokensBeforeSwap;
        
        if (!inSwapAndLiquify && swapAndLiquifyEnabled && to == uniswapV2Pair) {
            if (overMinimumTokenBalance) {
                contractTokenBalance = minimumTokensBeforeSwap;
                swapTokens(contractTokenBalance);    
            }
	        uint256 balance = address(this).balance;
            if (buyBackEnabled && balance > uint256(1 * 10**18)) {
                
                if (balance > buyBackUpperLimit)
                    balance = buyBackUpperLimit;
                
                buyBackTokens(balance.div(100));
            }
        }
        


  function afterPreSale() external onlyOwner {
        setSwapAndLiquifyEnabled(true);
        _taxFee = 3;
        _liquidityFee = 6;
        _devFee = 1;
        _maxTxAmount = 1000000 * 10**6 * 10**9;
    }
2

Just curious about if you have a presale function built in the contract. What does it look like?

3

I'm not entirely sure on how that works but i can show you the code i'm using.