• 11.4 baseline — 0.6 × season 11.4 (14 gm) + 0.4 × last 10 11.5
• +0.5 opponent leak — they concede 386.2/game vs a 369 league average
• +0.6 at this ground — averages 12 there (46 gm)
• vs them: averages 9.9 over 7 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.