W stands for WATS index, and is basically your 'level'. It gets higher as you earn more flags and stars. You can see the same number in your profile section. Up to 1.5, I think it is, it's shown to the nearest hundreth, however, once you go past 1.5, it just rounds to the nearest whole number.

K stands for karma, and starts off at 20. I don't know the exact formula, but it's basically the amount of stars and flags you've had, relative to the amount of posts you've made. So, the higher your star/flag count, in comparison to your post count, the higher your karma.