some question about flashloan?

[ocoderr]

Hi Julien
I watch you flashloan course, run the code .

I have some question about this code
`
if(arbInfo.direction == Direction.KyberToUniswap) {
//Buy ETH on Kyber
dai.approve(address(kyber), balanceDai);
(uint expectedRate, ) = kyber.getExpectedRate(
dai,
IERC20(KYBER_ETH_ADDRESS),
balanceDai
);
kyber.swapTokenToEther(dai, balanceDai, expectedRate);

      //Sell ETH on Uniswap
      address[] memory path = new address[](2);
      path[0] = address(weth);
      path[1] = address(dai);
      uint[] memory minOuts = uniswap.getAmountsOut(address(this).balance, path); 
      uniswap.swapExactETHForTokens.value(address(this).balance)(
        minOuts[1], 
        path, 
        address(this), 
        now
      );
    }

`
why sell all eth balance at uniswap?
Why not the quantity of eth bought from kybar in the previous step?