• 9.1 baseline — 0.6 × season 9.3 (16 gm) + 0.4 × last 10 8.7
• −0.1 opponent leak — they concede 211.7/game vs a 213.6 league average
• +0.0 at this ground — averages 9.1 there (18 gm)
• vs them: averages 6.5 over 2 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.