• 6.2 baseline — 0.6 × season 6.5 (12 gm) + 0.4 × last 10 5.7
• −0.6 opponent leak — they concede 494.6/game vs a 544.6 league average
• +13.7 at this ground — averages 19.9 there (12 gm)
• vs them: averages 28.0 over 2 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.