• 14.7 baseline — 0.6 × season 14.3 (16 gm) + 0.4 × last 10 15.3
• −1.0 opponent leak — they concede 343.2/game vs a 369 league average
• −3.5 at this ground — averages 11.3 there (28 gm)
• vs them: averages 5.5 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.