• 4.7 baseline — 0.6 × season 4.6 (9 gm) + 0.4 × last 10 4.8
• −0.1 opponent leak — they concede 210.3/game vs a 213.6 league average
• +2.1 at this ground — averages 6.7 there (43 gm)
• vs them: averages 5.8 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.