• 6.8 baseline — 0.6 × season 7.1 (17 gm) + 0.4 × last 10 6.3
• +0.1 opponent leak — they concede 189.9/game vs a 185.9 league average
• −1.7 at this ground — averages 5.1 there (12 gm)
• vs them: averages 6.7 over 6 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.