• 8.5 baseline — 0.6 × season 8.9 (16 gm) + 0.4 × last 10 8.0
• −0.1 opponent leak — they concede 364.1/game vs a 369 league average
• +2.3 at this ground — averages 10.8 there (10 gm)
• vs them: averages 6.7 over 3 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.