• 6.6 baseline — 0.6 × season 6.6 (19 gm) + 0.4 × last 10 6.6
• +0.5 opponent leak — they concede 230.1/game vs a 213.6 league average
• −0.1 at this ground — averages 6.5 there (31 gm)
• vs them: averages 8.8 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.