• 11.8 baseline — 0.6 × season 11.9 (20 gm) + 0.4 × last 10 11.7
• +0.0 opponent leak — they concede 369.9/game vs a 369 league average
• −2.3 at this ground — averages 9.5 there (4 gm)
• vs them: averages 9.8 over 5 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.