• 18.6 baseline — 0.6 × season 18.3 (18 gm) + 0.4 × last 10 19.0
• +0.3 opponent leak — they concede 375.7/game vs a 369 league average

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.