• 10.9 baseline — 0.6 × season 11.0 (12 gm) + 0.4 × last 10 10.7
• +0.9 opponent leak — they concede 399.5/game vs a 369 league average
• +0.5 at this ground — averages 11.4 there (5 gm)

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.