Initially, I use to think merit is by chance ( i.e something that will just happen) or lengthy article ( i.e writing too many paragraphs and the rest of them), but I have come to realize that, it is more than that.
I have being discouraged several times because of my numerous posts and replies yet no merit then. Even now, some times I use to be discourage. However, the only way to get merit is by posting quality article ( that is what determines merit) which almost everybody is aware of now.
In summary, don't look at the quantity of post you have make so far but instead try to adjust, I mean improve in your posts, above all be consistent and patient that is the key.
If you only prioritize the length of writing and the number of posts to get merit then you will never get it at all. From what i have noticed, when your account has an attractive reputation, you will easily get "merit", for example if you are active on WO board or Bitcoin technical then you will easily get merit, the point is that you don't create chaos, make disturbing posts or make posts that are personally insulting then your account will get good merit even though the number of posts in your post is short.