In MN10, the Buddha points out that there are four steps to mindfulness meditation:
MN10:1.6: The Buddha said this:
MN10:2.1: “Mendicants, the four kinds of mindfulness meditation are the path to convergence. They are in order to purify sentient beings, to get past sorrow and crying, to make an end of pain and sadness, to end the cycle of suffering, and to realize extinguishment.
The third step is mindfulness of the mind, which includes thoughts:
MN10:3.1: What four?
MN10:3.2: It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.3: They meditate observing an aspect of feelings—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.4: They meditate observing an aspect of the mind—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.5: They meditate observing an aspect of principles—keen, aware, and mindful, rid of desire and aversion for the world.
Notice that a repeated phrase is "rid of desire and aversion for the world". When there is desire, we see what we want to see. When there is aversion, we avert our mind away from what is. Without desire and aversion we witness and remember what is:
DN34:2.1.20: Furthermore, a mendicant is mindful. They have utmost mindfulness and alertness, and can remember and recall what was said and done long ago.
The number "one" is a thought. The number "two" is a thought. When we count breaths (an aspect of the body) we are witnessing our breaths and being mindful of the count. So in counting the breaths we witness the count increase with our breaths.
Between "one" and "two" there is a silent thread that holds and moves with the count. The thought of "one" takes but a moment, but a breath is longer than a moment, so there needs to be a mindful, ephemeral bridge from "one" to "two". Following that thread, the count proceeds. Losing that thread, the count is lost.
Thoughts are an aspect of the mind. The silent thread is an aspect of the mind. There are other aspects.
“Witnessing is not a thought, but you can start thinking about witnessing, you can make it a thought. The moment you make it a thought, it is no longer witnessing. Either it is witnessing or it is a thought; it cannot be both together. OshoTimes