• 22.4 baseline — 0.6 × season 21.4 (20 gm) + 0.4 × last 10 24.0
• +1.2 opponent leak — they concede 389.2/game vs a 369 league average
• −4.7 at this ground — averages 17.8 there (4 gm)
• vs them: averages 19.3 over 3 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.