• 11.9 baseline — 0.6 × season 11.8 (11 gm) + 0.4 × last 10 11.9
• +0.0 opponent leak — they concede 369.9/game vs a 369 league average
• +0.0 at this ground — averages 11.9 there (7 gm)
• vs them: averages 9.9 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.