Also - if you earn more than £49k then tick the £49k box.
When it comes to money I think of myself as
When compared to the people I spend most of my time with I am
My income is equal to or less than (£weekly/£yearly/$yearly)
Those figures are the income percentiles for the fully employed UK workers, which you can get from here. If you're in the second group (£312 a week) then at least 10% of the population earn less than you, if you're in the third group then at least 20% of the population earns less than you. If you're in the first group then your life sucks.
Thanks to red_phil for the link.