• 3.8 baseline — 0.6 × season 3.6 (7 gm) + 0.4 × last 10 4.1
• +0.0 opponent leak — they concede 155.9/game vs a 155.4 league average
• +0.7 at this ground — averages 4.5 there (34 gm)
• vs them: averages 4.0 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.