• 10.6 baseline — 0.6 × season 10.3 (20 gm) + 0.4 × last 10 11.1
• +0.8 opponent leak — they concede 230.1/game vs a 213.6 league average
• −1.1 at this ground — averages 9.5 there (51 gm)
• vs them: averages 9.4 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.