• 9.7 baseline — 0.6 × season 9.8 (20 gm) + 0.4 × last 10 9.6
• +0.2 opponent leak — they concede 378.4/game vs a 369 league average
• −1.2 at this ground — averages 8.4 there (9 gm)
• vs them: averages 10.2 over 5 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.