• 11.7 baseline — 0.6 × season 12.0 (6 gm) + 0.4 × last 10 11.2
• +0.6 opponent leak — they concede 389.2/game vs a 369 league average
• +2.4 at this ground — averages 14.1 there (10 gm)
• vs them: averages 13.3 over 10 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.