• 15.0 baseline — 0.6 × season 15.1 (9 gm) + 0.4 × last 10 14.8
• +0.0 opponent leak — they concede 369.9/game vs a 369 league average
• +0.3 at this ground — averages 15.3 there (8 gm)
• vs them: averages 9.5 over 2 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.