• 22.9 baseline — 0.6 × season 23.1 (20 gm) + 0.4 × last 10 22.6
• +1.3 opponent leak — they concede 389.2/game vs a 369 league average
• −5.7 at this ground — averages 17.2 there (17 gm)
• vs them: averages 17.4 over 13 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission. Round 9: 5 — far outside his usual range; kept in the average, not smoothed away.