• 10.4 baseline — 0.6 × season 10.5 (16 gm) + 0.4 × last 10 10.2
• −0.5 opponent leak — they concede 203.2/game vs a 213.6 league average
• +1.0 at this ground — averages 11.3 there (38 gm)
• vs them: averages 13.1 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.