Swap event sometimes emits amount different by 1 to the actual transfer amount

[DenyVeyten]

Example: https://etherscan.io/tx/0x30168805aaa7b9b0731362fd3a3a689dc686b41992e0936f957556d54c20934f#eventlog#174

Balance of token1 before and after swap for pool address matches transfer amount and differs with swap amount by 1

In other cases the difference can be much bigger (diff by 1 for USDT and by a lot for WETH):
https://etherscan.io/tx/0x6621d9f7e55ea6656933742493a2bae68630ceb258a0c44de388f2d01ee21a18#eventlog