• 7.8 baseline — 0.6 × season 8.2 (17 gm) + 0.4 × last 10 7.2
• +0.4 opponent leak — they concede 225.5/game vs a 213.6 league average
• +0.4 at this ground — averages 8.2 there (10 gm)
• vs them: averages 8.0 over 1 game — 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.