• 111.9 baseline — 0.6 × season 113.2 (20 gm) + 0.4 × last 10 110.1
• −9.1 opponent leak — they concede 1550.3/game vs a 1687.8 league average
• +11.1 at this ground — averages 123 there (39 gm)
• vs them: averages 120.3 over 9 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.