Alliosis I think the most important criteria to be offered a contract is quality of the work itself. For example, there's this one story that I've been following since it was first posted. Last week, the story's gift function became available. So I could only assume that it got contracted. The author's update is super unstable. There was a time that she only posted two updates a month. But despite that, she has loyal readers (including me lol). During the time that her updates were slow and all over the place, she never go below top 300 in the power rankings. Her novel probably got contracted around chapter 30 something. Now, her updates became more stable. She actually promised us readers 3chaps a week. And we're already super happy at that because we already experienced the two updates a month. 3chaps a week is a super upgrade. I guess because she got contracted, she finally felt a bit responsible. LOL.
Her writing quality is really good. That's why I think she got contracted. So sometimes it's not really about the quantity of the chaps you release. If you post two chaps a day but the quality is not that good, then it probably won't go anywhere. Quality is always better than quantity. As a reader, that's more important for me.
Good luck with your writing, author-san!