• 9.0 baseline — 0.6 × season 8.8 (14 gm) + 0.4 × last 10 9.3
• +0.2 opponent leak — they concede 158.8/game vs a 155.4 league average
• +0.0 at this ground — averages 9 there (9 gm)
• vs them: averages 8.0 over 1 game — 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.