• 0.3 baseline — 0.6 × season 0.3 (12 gm) + 0.4 × last 10 0.3
• −0.1 opponent leak — they concede 6.8/game vs a 9.4 league average
• −0.2 at this ground — averages 0.1 there (50 gm)
• vs them: averages 0.0 over 5 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.