Go with your first thought
If you just went for a hike and your knee feels sore, pick the number that matches how it feels right now. There is no need to adjust up or down for what you were doing.
Your clinician wants an honest snapshot at each time point. Overthinking usually makes the data less useful, not more.
On a pain slider from 0 (no pain) to 10 (worst pain), drag or tap the number that fits how you feel in this moment.