The counting has a number of really useful functions (almost as useful as the breathing, really!).
It’s very easy just to “space out” instead of actually meditating. When we space out we get distracted without realizing it. The counting helps to give us a more objective sense of how much of the time we’re distracted, and how much we’re remaining aware.
Counting allows us to “measure” how long we’re maintaining our awareness. Sometimes it’s hard to stay focused on the breath even for three breaths. Other times we can be aware for several cycles of ten breaths. So you can tell if it’s a “good day” or a “bad day.”
Counting gives us something to aim for. It’s good to have goals. If you’re getting distracted before getting to the tenth breath then you can try hard to reach ten. If you make it that far then you can try to get to ten again. Without the counting it’s hard to have any sense of what you’re working towards.
The numbers help us to see if we’re making progress. If you put the effort into your meditation practice then you’ll see results. But how can you see results if there’s nothing to measure them by?
The numbers subtly alter your perception of the breath. When you count after the out-breath then that’s the part of the breathing process that you’re most aware of. So in the first stage of the practice you’re more aware of breathing out. We’ll talk more about this after you’ve done the second stage of the practice.