• 11.6 baseline — 0.6 × season 11.6 (11 gm) + 0.4 × last 10 11.6
• +0.5 opponent leak — they concede 386.2/game vs a 369 league average
• −0.6 at this ground — averages 11 there (21 gm)
• vs them: averages 12.5 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.