• 7.9 baseline — 0.6 × season 8.0 (15 gm) + 0.4 × last 10 7.8
• +0.4 opponent leak — they concede 389.2/game vs a 369 league average
• +4.4 at this ground — averages 12.3 there (10 gm)
• vs them: averages 10.4 over 7 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.