In the breath counting meditation I practiced, the count starts from 1 and goes up to 10. After every breath (inhalation and exhalation together), the count goes up by 1. If the attention wanders from the breath, when we become aware of this, we start counting from 1 again. If we go up to 10, we start from 1 again.
The point of counting, is to have a mental reference point that you are actually meditating, and for you to realize better when your attention has wandered or is wandering a lot. It is basically a reminder of focusing, a reminder that you are meditating. This is beneficial for particularly active minds, because when just focusing on the breath, the mind can lose focus for extended periods of time and the person can lose awareness of this and can get lost in their thoughts/emotions/etc.
Basically, counting in this context is an intentional activity to support our meditation, to cultivate concentration. Therefore, it doesn’t matter until which number you count, but that you intentionally determine this from the beginning, and stay consistent throughout your meditation sessions. Don’t use the number to increase or decrease the tempo of breathing; for example, if you are meditating for a fixed duration, if you select a large number, you will need to breath quicker to reach this number, or if you select a small number then your breaths will need to be deep. The number itself is not the goal here. The breath has a natural tempo associated with the mind’s current state. We don’t artificially modify this tempo in breath awareness meditations where we focus on the breath and stay aware. I once had meditated with a count to 100, and it worked, too. The intention and the focus while meditating is what is important. If we intentionally cultivate a dedication, supporting our practice any way we can and keep practicing, our practice will evolve more quickly.
Here are some useful resources that accurately teach meditation:
(Concise and accurate definition of meditation and how to practice, including advice for difficulties during meditation)
(Contains breath counting meditation guidance)