• 10.7 baseline — 0.6 × season 10.7 (20 gm) + 0.4 × last 10 10.7
• −0.6 opponent leak — they concede 201.8/game vs a 213.6 league average
• +1.2 at this ground — averages 11.9 there (86 gm)
• vs them: averages 10.9 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.