• 7.0 baseline — 0.6 × season 6.8 (20 gm) + 0.4 × last 10 7.2
• −0.8 opponent leak — they concede 82.1/game vs a 93.4 league average
• −1.5 at this ground — averages 5.5 there (47 gm)
• vs them: averages 5.0 over 4 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.