• 15.0 baseline — 0.6 × season 14.9 (13 gm) + 0.4 × last 10 15.2
• −0.1 opponent leak — they concede 367.1/game vs a 369 league average
• +0.0 at this ground — averages 15.1 there (37 gm)
• vs them: averages 12.1 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.