• 11.5 baseline — 0.6 × season 11.8 (18 gm) + 0.4 × last 10 11.2
• −0.2 opponent leak — they concede 210.3/game vs a 213.6 league average
• −2.3 at this ground — averages 9.2 there (14 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.