• 14.1 baseline — 0.6 × season 13.8 (18 gm) + 0.4 × last 10 14.5
• +0.3 opponent leak — they concede 377.9/game vs a 369 league average
• −2.6 at this ground — averages 11.5 there (51 gm)
• vs them: averages 13.5 over 6 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.