I believe that Icopress can explain that better than us and if he takes part in this thread then that will be very helpful for @OP and all those members who don't really understand that warning fully.
I don't think that particular statement needs any extra explanation, it is pretty straightforward and easy to understand for the campaign participants that it may concern, just don't make too many posts in such a short space of time, it then becomes worse when the posts are of very low quality. CM's would definitely prefer posts that are spread out, but they wouldn't mind users making many high quality posts in quick succession, especially when the participant makes posts above the number the campaign pays for.