• 16.3 baseline — 0.6 × season 16.1 (20 gm) + 0.4 × last 10 16.7
• +0.1 opponent leak — they concede 156.4/game vs a 155.4 league average
• −1.3 at this ground — averages 15 there (48 gm)
• vs them: averages 13.4 over 9 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.