• 6.7 baseline — 0.6 × season 6.6 (16 gm) + 0.4 × last 10 6.8
• −0.2 opponent leak — they concede 181.3/game vs a 185.9 league average
• −0.6 at this ground — averages 6.1 there (48 gm)
• vs them: averages 7.2 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.