Printing as many numbers as possible in 9 seconds then a "-1" at the 10th second

So, I'm interested in printing as many numbers as possible in 9 seconds then printing a -1 at the 10th second. I have a while loop to print -1 every 10 seconds and a while loop to print any random number between 0 and 10 every 9 seconds. 1

My problem is twofold:

1. I'm not sure how to create a loop which can print as many possible numbers (depending on computing speed) in 9 seconds
2. I'm not sure how to put that together with the loop to print -1 every 10 seconds.

Thanks so much everyone!