• 4.2 baseline — 0.6 × season 4.6 (5 gm) + 0.4 × last 10 3.6
• +0.0 opponent leak — they concede 156.4/game vs a 155.4 league average
• −0.5 at this ground — averages 3.7 there (17 gm)
• vs them: averages 4.5 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.