• 10.0 baseline — 0.6 × season 9.7 (13 gm) + 0.4 × last 10 10.5
• −0.6 opponent leak — they concede 345.4/game vs a 369 league average
• +1.2 at this ground — averages 11.3 there (8 gm)
• vs them: averages 13.6 over 10 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.