• 6.2 baseline — 0.6 × season 6.5 (12 gm) + 0.4 × last 10 5.7
• −0.0 opponent leak — they concede 544.7/game vs a 545.7 league average
• +13.7 at this ground — averages 19.9 there (12 gm)
• vs them: averages 15.0 over 1 game — 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.