How get posts for category with offset?

for example in category “news” of my blog there are 50 posts. For get last 10 posts I do: http://mywordpress.com/?json=get_category_posts&slug=news&count=10&status=publish And it work correctly. Now I want to get my posts from 11 to 20 skipping last 10 posts, etc. How can I do?

http://ww.wp.xz.cn/plugins/json-api/