• 6.9 baseline — 0.6 × season 7.0 (19 gm) + 0.4 × last 10 6.8
• +0.6 opponent leak — they concede 233.1/game vs a 213.6 league average
• +1.4 at this ground — averages 8.3 there (51 gm)
• vs them: averages 8.2 over 11 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.