child tax credits, getting too little?

Hi all I am wandering if I am receiving the correct amount of child tax credits?

I worked up until August last year and since then I have been getting £238 a month (me, partner both out of work on JSA currently and 1 child).

This month it went up to £249 so I thought I should double check it all and the official calculator says I should get £3153.92 a year.

That's £262 a month (it is over 12 months right?).