• 0.3 baseline — 0.6 × season 0.2 (20 gm) + 0.4 × last 10 0.4
• +0.0 opponent leak — they concede 26.7/game vs a 23.6 league average
• −0.2 at this ground — averages 0.1 there (56 gm)
• vs them: averages 0.3 over 12 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.