• 14.6 baseline — 0.6 × season 14.2 (17 gm) + 0.4 × last 10 15.2
• +0.6 opponent leak — they concede 193.8/game vs a 186.3 league average
• −4.1 at this ground — averages 10.5 there (4 gm)
• vs them: averages 10.5 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.