Import only income and ignore outgoings?

I need to import only incoming payments across 4 different accounts and ignore any outgoings. I tried configuring each account by clicking on the ‘payee’ tab, enabling ‘advanced’ and using the example template of it.transactionAmount.amount > 0 ? (which looked like it might work) but the preview looks like this, so I guess not:

I also tried it.transactionAmount.amount > 0 (without the trailing question mark) which didn't produce the same errors, but also didn’t filter any outgoings from the preview:

Any ideas how do to this?

btw I’m not at all familiar with that JS template syntax being used. I’ve never seen it before otherwise I’d stab around trying things, but in this case I’m not even sure where to start.