• 9.7 baseline — 0.6 × season 9.8 (20 gm) + 0.4 × last 10 9.6
• +0.5 opponent leak — they concede 164/game vs a 155.4 league average
• +1.0 at this ground — averages 10.7 there (34 gm)
• vs them: averages 12.0 over 10 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.