• 10.6 baseline — 0.6 × season 10.6 (20 gm) + 0.4 × last 10 10.6
• −0.4 opponent leak — they concede 150.3/game vs a 155.4 league average
• −0.6 at this ground — averages 10 there (90 gm)
• vs them: averages 9.6 over 8 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.