• 10.7 baseline — 0.6 × season 10.1 (20 gm) + 0.4 × last 10 11.5
• −0.3 opponent leak — they concede 357.8/game vs a 369 league average
• −2.0 at this ground — averages 8.6 there (21 gm)
• vs them: averages 8.0 over 2 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.