Or they pulled in 18 million over the past year but their monthly revenue is now higher, and thus on a growth trajectory to pull in much more than 18 million next year.
This also doesn't include advertising revenue to their 20 million user base.
And it's a startup... so you know, the whole idea is that it might make more in the future. I know it is a lot of money, but they are supporting 20 million users & 8 million active.