• 1.5 baseline — 0.6 × season 2.0 (17 gm) + 0.4 × last 10 0.8
• +0.2 opponent leak — they concede 26.6/game vs a 23.7 league average
• −1.1 at this ground — averages 0.4 there (5 gm)
• vs them: averages 2.2 over 9 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.