• 136.6 baseline — 0.6 × season 139.6 (12 gm) + 0.4 × last 10 132.0
• −11.1 opponent leak — they concede 1550.3/game vs a 1687.8 league average
• −8.1 at this ground — averages 128.5 there (4 gm)
• vs them: averages 113.3 over 6 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.