• 14.5 baseline — 0.6 × season 14.1 (15 gm) + 0.4 × last 10 15.2
• −0.5 opponent leak — they concede 180.1/game vs a 186.3 league average
• −1.1 at this ground — averages 13.4 there (5 gm)
• vs them: averages 12.9 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.