• 0.4 baseline — 0.6 × season 0.3 (20 gm) + 0.4 × last 10 0.5
• −0.0 opponent leak — they concede 35.4/game vs a 35.7 league average
• +0.4 at this ground — averages 0.8 there (68 gm)
• vs them: averages 0.6 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.