Yeah, densities and fuzzy matching. It'll get more intelligent eventually, but does a pretty good job on common ingredients at the moment.

It'd be good if you could customise what kinds of foods should be displayed in what measurements.

E.g. I'm seeing 1 cup of steamed rice - being British I have no idea what that means. I turn metric on and it tells me 237 milliliters of rice, whereas I would be expecting grams. I'm pretty sure measuring solids by volume is a US-only thing.