• 3.8 baseline — 0.6 × season 4.2 (20 gm) + 0.4 × last 10 3.2
• −0.0 opponent leak — they concede 93.2/game vs a 93.4 league average
• +1.8 at this ground — averages 5.6 there (78 gm)
• vs them: averages 5.0 over 9 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.