• 7.5 baseline — 0.6 × season 7.1 (20 gm) + 0.4 × last 10 8.2
• −0.1 opponent leak — they concede 210.3/game vs a 213.6 league average
• −2.8 at this ground — averages 4.8 there (9 gm)
• vs them: averages 5.5 over 4 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.