Am I right in thinking that you can work up to 16 hours a week on Job Seekers?

I was under the impression that you could actually work up to 16 hours a week :P I was on Job Seeker's and got a job working less than 16 hours, which I declared to the Job Centre. However, when I declared this they told me that because I was making, literally, a couple of pound more than the "recommended weekly allowance a person can live on", that my JS would be stopped. Does anyone know if they judge your allowance on hours or pay? :)