• 9.6 baseline — 0.6 × season 9.6 (14 gm) + 0.4 × last 10 9.7
• −0.6 opponent leak — they concede 200.8/game vs a 213.6 league average
• −1.2 at this ground — averages 8.4 there (10 gm)
• vs them: averages 9.2 over 6 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.