• 10.3 baseline — 0.6 × season 10.4 (8 gm) + 0.4 × last 10 10.3
• +0.4 opponent leak — they concede 160.7/game vs a 155.4 league average
• −1.0 at this ground — averages 9.4 there (31 gm)
• vs them: averages 9.8 over 4 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.