• 8.1 baseline — 0.6 × season 8.3 (20 gm) + 0.4 × last 10 7.9
• +0.4 opponent leak — they concede 224.7/game vs a 213.6 league average
• +2.8 at this ground — averages 10.9 there (85 gm)
• vs them: averages 11.1 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.