Wandering is expected. The useful skill is recognising it and returning without a verdict.
Recognise the moment
You may become aware that you have been planning, remembering or evaluating the practice. That moment of recognition is useful information. There is no need to calculate how long you were distracted.
Use a small label
Try a neutral word such as thinking or planning. Use it once, then notice a comfortable breath, sound, visible detail or contact point. If naming thoughts becomes distracting, skip the label and return directly.
Make the task smaller
Instead of trying to stay attentive for a whole recording, notice the next single breath or sound. Then begin again. A clear, manageable instruction is easier to use than demanding continuous concentration.
Avoid turning it into a score
A busy session is still a session in which you practised noticing. My progress records what you did; it does not measure how calm or empty your mind became. Choose one practical adjustment for next time, such as a different anchor or a shorter lesson.
General wellbeing guidance from Mahonie. Adapt or stop any practice when you prefer.