The Gateway Asset Amount currently rounds to the hundredths. Some assets like ETH need more specificity, and rounding to the thousandths or ten thousandths.

For example, I fast bridge .10 ETH. I ended up receiving .0999 ETH.

The Gateway shows that I have .10 ETH:

When I try to bridge to L2, it tells me the max amount is .100 ETH, but when I enter .1 ETH, it tells me it has to be less than .100 ETH.

It is a bit of nuisance having to look at a separate tab or window to determine the exact amount I have.