• 13.7 baseline — 0.6 × season 13.5 (11 gm) + 0.4 × last 10 13.9
• +0.3 opponent leak — they concede 378.4/game vs a 369 league average
• +0.6 at this ground — averages 14.3 there (7 gm)

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.