The Mon Projet system has no authority. The government decides when they want to stop accepting people. 5.000 is just the minimum they promised to accept. On top of that they will know how many applicants will actually come to canada from last intake period and now accept enough to actually reach 5000 people coming to canada, instead of just submitting a form... On top of that they might be just generous. Let's see what they say tomorrow.
Plus, I was one of the first to submit and got around 7000 as application number. So with 12000 we are likely looking at the end of it. That would make around 6k for June and 6k for August... And also keep in mind that all people outside of this limited quota program also get their number... So there might also be a few hundred to thousand people in those 12000 that have a job offer for instance.