• 22.3 baseline — 0.6 × season 21.9 (20 gm) + 0.4 × last 10 23.0
• +0.4 opponent leak — they concede 375.7/game vs a 369 league average
• +0.4 at this ground — averages 22.7 there (70 gm)
• vs them: averages 21.0 over 12 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.