• 10.8 baseline — 0.6 × season 10.8 (20 gm) + 0.4 × last 10 10.7
• −0.2 opponent leak — they concede 210.3/game vs a 213.6 league average
• +1.7 at this ground — averages 12.4 there (18 gm)
• vs them: averages 11.7 over 10 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.