Makkale, I need some help with myth busting

I recently moved out of Perungudi to Porur. I hate mosquitos, and I’ve made it a point to not have any mosquitos in my apartment. I had my perima come over yesterday, she had the windows open in the room she was about to sleep in. I asked her to have the window closed if she wanted the mosquitoes to not bother her. To my surprise she told me something I’m not sure if it’s true. “Kosu 6 - 7 maniku than pa varum. 9 maniku mela veetuku varathu pa” I laughed it off saying that wasn’t true and I had just gotten bit by a mosquito. My perima insisted that the mosquitoes that have found asylum before 7PM in my apartment will continue to stay on hunt but no new outsider kosu will enter at that time. I didn’t want to argue and let my perima sleep since virumthombal is important. But, I do not think that’s true and I’d like to hear your take on this.