• 11.0 baseline — 0.6 × season 10.6 (15 gm) + 0.4 × last 10 11.7
• −0.3 opponent leak — they concede 357.8/game vs a 369 league average
• −4.2 at this ground — averages 6.8 there (5 gm)
• vs them: averages 7.4 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.