• 11.2 baseline — 0.6 × season 11.4 (15 gm) + 0.4 × last 10 10.8
• −0.3 opponent leak — they concede 360.2/game vs a 369 league average
• −2.6 at this ground — averages 8.6 there (18 gm)
• vs them: averages 14.5 over 2 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.