• 9.6 baseline — 0.6 × season 9.6 (10 gm) + 0.4 × last 10 9.6
• +0.0 opponent leak — they concede 213.7/game vs a 213.6 league average
• −2.6 at this ground — averages 7 there (5 gm)
• vs them: averages 8.6 over 9 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.