In most cases, when you hear the word count referring to math, you think of adding 1 repeatedly to a number. As in, 1, 2, 3, 4 and so on, up you go up to the destination of 10 or 100. This skill is part of a group of concepts we call Number Sense.
A variation on this process is called counting down. My hunch is that it's actually performed more often than counting up. It works just the same way, only you start with 10, 9, 8, 7 and so on down to zero, then you shout "Start the Movie" or BLAST-OFF! or READY OR NOT, HERE I COME!
For me counting down will always be associated with the launch of rockets at Cape Canaveral in Florida.
There is specific language that evolved just for these rocket launch attempts. Go here to see NASA explanation of a countdown. It begins with the term T-minus which stands for Launch Time minus so many hours or minutes.
The announcer would say T-minus 2 minutes and counting ... and so on down to about 20 seconds, then go continuously down to zero (with a lot of noise going on in the background). Then whoosh!
If you have the right job at NASA, you can get paid for counting down. It's a useful skill learned in elementary math class. Of course, even if you never grow up, you can keep playing with rockets.