• 22.6 baseline — 0.6 × season 23.1 (19 gm) + 0.4 × last 10 21.9
• +0.6 opponent leak — they concede 378.4/game vs a 369 league average
• −4.9 at this ground — averages 17.7 there (68 gm)
• vs them: averages 20.5 over 8 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.