The numbering is common across JAA
And thus broadly follows the original sequence numbers used by the Royal Air Force during and maybe even before World War 2. Published in RAF Air Publication A.P 3225.
Sequence 1. Familiarisation.
2. Preparation for Flight.
3. Air Experience.
4. Effects of Controls.
5. Control of aircraft on ground.
6. Straight and Level.
7. Climbing and Descending.
8. Stalling.
9. Turning.
10. Spinning.
11. Take off and climb downwind position.
12. Approach and Landing.
13. First solo.
14. Consolidation period.
15. Instrument/weather procedure.
16. Low flying.
17. Forced landings.
18. Aerobatics.
19. Night flying.
20. Pilot navigation.
21. Formation flying.
History is indeed facinating.