• 9.4 baseline — 0.6 × season 9.0 (5 gm) + 0.4 × last 10 9.9
• −0.2 opponent leak — they concede 152.3/game vs a 155.4 league average
• +4.8 at this ground — averages 14.2 there (49 gm)
• vs them: averages 17.0 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.