• 9.0 baseline — 0.6 × season 9.0 (11 gm) + 0.4 × last 10 9.1
• +0.2 opponent leak — they concede 219.2/game vs a 213.6 league average
• +1.5 at this ground — averages 10.5 there (4 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.