• 4.1 baseline — 0.6 × season 4.1 (13 gm) + 0.4 × last 10 4.2
• −0.0 opponent leak — they concede 35.4/game vs a 35.7 league average
• −0.1 at this ground — averages 4 there (23 gm)
• vs them: averages 4.0 over 2 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.