• 9.8 baseline — 0.6 × season 9.9 (14 gm) + 0.4 × last 10 9.7
• −0.2 opponent leak — they concede 360.2/game vs a 369 league average
• +2.1 at this ground — averages 11.9 there (70 gm)
• vs them: averages 13.9 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.