• 4.0 baseline — 0.6 × season 4.0 (12 gm) + 0.4 × last 10 4.1
• +0.6 opponent leak — they concede 106.2/game vs a 93.4 league average
• +1.1 at this ground — averages 5.2 there (6 gm)
• vs them: averages 4.5 over 6 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.