• 4.0 baseline — 0.6 × season 3.9 (7 gm) + 0.4 × last 10 4.1
• +0.1 opponent leak — they concede 219.2/game vs a 213.6 league average
• +0.1 at this ground — averages 4.1 there (10 gm)
• vs them: averages 2.0 over 1 game — 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.