• 4.7 baseline — 0.6 × season 4.9 (9 gm) + 0.4 × last 10 4.4
• +0.1 opponent leak — they concede 35.9/game vs a 35.3 league average
• −0.8 at this ground — averages 3.9 there (26 gm)
• vs them: averages 2.3 over 3 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.