• 10.1 baseline — 0.6 × season 10.7 (20 gm) + 0.4 × last 10 9.3
• −0.5 opponent leak — they concede 203.2/game vs a 213.6 league average
• +2.0 at this ground — averages 12.1 there (106 gm)
• vs them: averages 12.2 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.