• 6.6 baseline — 0.6 × season 7.1 (18 gm) + 0.4 × last 10 6.0
• +0.6 opponent leak — they concede 101.3/game vs a 93.4 league average
• −0.7 at this ground — averages 6 there (78 gm)
• vs them: averages 6.2 over 13 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.