• 10.8 baseline — 0.6 × season 11.1 (16 gm) + 0.4 × last 10 10.4
• −0.5 opponent leak — they concede 203.2/game vs a 213.6 league average
• −1.5 at this ground — averages 9.3 there (65 gm)
• vs them: averages 11.0 over 4 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.