• 11.7 baseline — 0.6 × season 11.7 (19 gm) + 0.4 × last 10 11.6
• +0.3 opponent leak — they concede 219.6/game vs a 213.6 league average
• −1.0 at this ground — averages 10.7 there (68 gm)
• vs them: averages 13.6 over 8 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.