• 8.0 baseline — 0.6 × season 8.1 (17 gm) + 0.4 × last 10 7.8
• +0.6 opponent leak — they concede 230.1/game vs a 213.6 league average
• −0.9 at this ground — averages 7.1 there (44 gm)
• vs them: averages 5.8 over 5 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.