What is this value supposed to be, where is it used?

[gigamesh]

What is this value supposed to be, where is it used?

I think this should only result in an error if a user tries to withdraw, because they'd be attempting to withdraw from an address without a balance.

l2Receipt = await contracts.l2.bridge.connect(signer).withdraw(contracts.l2.token.address, amount, 0, '0x');