• 7.1 baseline — 0.6 × season 6.7 (20 gm) + 0.4 × last 10 7.8
• +0.2 opponent leak — they concede 36.6/game vs a 35.7 league average
• −1.7 at this ground — averages 5.4 there (32 gm)
• vs them: averages 4.3 over 3 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.