• 10.1 baseline — 0.6 × season 10.1 (15 gm) + 0.4 × last 10 10.1
• −0.9 opponent leak — they concede 141.4/game vs a 155.4 league average
• +4.6 at this ground — averages 14.8 there (8 gm)
• vs them: averages 15.2 over 6 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.