Ventilation In/Out Question

Hey guys, my first grow. My tent is 16'x8'. Local shop sold me 8" inlet fan and 10" outlet fan, plus shroom filter for the intake. First time I turned both of them on, I was in the tent, and good thing I was there, because the 10" fan created so much suction that walls of the tents started to implod. I almost lost the tent, if I did not open zipper doors in time, tent would definitely collapse.
Now I run inlet fan (8" one) on a full speed, while outlet fan only running at its lowest level - at 35%.
Hence, question, why the heck the store sold me such difference in fans? Is 10" outlet fan overkill for my tent? Should I have got another 8" outlet fan to match the intake fan?
If I add carbon filter in the future, will it slow down the amount of air outlet fan sucks out of the tent? Is it possible that the store sold me bigger outlet fan to match intake speeds once carbon filter added to the outlet?

Usually negative pressure is a good thing if you're using a carbon filter to prevent the smell of your sweet juicy marijuana plant reaching unwanted noses.
If its imploding, it sounds like a bad qualilty tent or you didn't put it up right or that outlet fan is insanely strong.