• 5.2 baseline — 0.6 × season 5.2 (6 gm) + 0.4 × last 6 5.2
• +0.1 opponent leak — they concede 219.6/game vs a 213.6 league average
• +0.8 at this ground — averages 6 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.