How strict is Columbia towards deadlines?

I’m a junior in high school and applied for the Columbia Science Honors Program (SHP). Although I am not an absolute genius when it comes to math or science, I do very well in them and have a great interest in both fields. However due to several sudden problems occurring both at home and outside (I personally don’t like to make excuses), I only recently informed my guidance counselor of the address to send the transcript of my grades that is required for the application process on March 15. The deadline is March 17 and I am afraid that my admission will be nullified because of my lateness. The transcript must be mailed. This is completely my fault, I admit this wholeheartedly. But I would like to know how Columbia University would respond to my error?

usually if sent out before deadline it will be fine

but what happens if they get it after the deadline @j417872

Usually the deadline is met if mail is postmarked by that date.