• 0.1 baseline — 0.6 × season 0.1 (10 gm) + 0.4 × last 10 0.1
• +0.0 opponent leak — they concede 13.5/game vs a 12.2 league average
• +0.2 at this ground — averages 0.3 there (15 gm)

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.