• 152.3 baseline — 0.6 × season 146.6 (19 gm) + 0.4 × last 10 160.9
• +13.6 opponent leak — they concede 1838.8/game vs a 1687.8 league average
• −52.6 at this ground — averages 99.8 there (8 gm)
• vs them: averages 74.3 over 4 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.