• 9.6 baseline — 0.6 × season 9.2 (20 gm) + 0.4 × last 10 10.2
• +0.7 opponent leak — they concede 166.4/game vs a 155.4 league average
• −1.3 at this ground — averages 8.3 there (16 gm)
• vs them: averages 10.7 over 7 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.