After the skipped DEX callback, we are looking at this piece of code:
If you remember, memVar2_ was calculated as deposit + payback amount, so its purpose was for this check, where we want to make sure the caller has sent enough native token:
memVar2_ > msg.value
But also not too much above the excess allowance limit:
msg.value > (memVar2_ * (FOUR_DECIMALS + memVar3_)) / FOUR_DECIMALS
Where:
memVar3_ = 100; // MAX_INPUT_AMOUNT_EXCESS = 1%
FOUR_DECIMALS = 1e4;
// 10100 / 10000 = 1.01
So this simply reverts if we sent 1% more native token than the combined deposit plus payback amount passed in the function call, to prevent the caller from accidentally passing more tokens than needed.
Also, one subtle detail needed for the next step: we are resetting the memVar2_ value to zero.