Income on UW Application Form?

The form asks for gross annual income. Is this referring to adjusted gross, W-2 total (line 7), or taxable income?

Also: I’m entering info from 2016 and 2017, as 2018’s taxes haven’t been filed yet, but the form says I can enter an “estimate” for the most recent year. Should I do this? It would be easier to just use 16/17.