• 11.1 baseline — 0.6 × season 11.4 (19 gm) + 0.4 × last 10 10.6
• −0.5 opponent leak — they concede 353.4/game vs a 369 league average
• −1.5 at this ground — averages 9.6 there (28 gm)
• vs them: averages 7.0 over 3 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.