• 9.7 baseline — 0.6 × season 9.7 (10 gm) + 0.4 × last 10 9.7
• +0.3 opponent leak — they concede 219.2/game vs a 213.6 league average
• −2.5 at this ground — averages 7.2 there (13 gm)
• vs them: averages 7.0 over 1 game — 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.