• 16.9 baseline — 0.6 × season 16.8 (20 gm) + 0.4 × last 10 17.1
• −0.3 opponent leak — they concede 209.2/game vs a 213.6 league average
• −3.0 at this ground — averages 13.9 there (47 gm)
• vs them: averages 16.3 over 8 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.