• 8.0 baseline — 0.6 × season 7.8 (15 gm) + 0.4 × last 10 8.2
• −0.5 opponent leak — they concede 345.4/game vs a 369 league average
• +1.3 at this ground — averages 9.2 there (9 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.