• 7.5 baseline — 0.6 × season 7.1 (7 gm) + 0.4 × last 10 8.1
• +0.2 opponent leak — they concede 378.4/game vs a 369 league average
• +3.8 at this ground — averages 11.3 there (10 gm)
• vs them: averages 11.1 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.