• 18.0 baseline — 0.6 × season 17.7 (19 gm) + 0.4 × last 10 18.3
• −0.3 opponent leak — they concede 363.9/game vs a 369 league average
• −7.2 at this ground — averages 10.8 there (4 gm)
• wet forecast: too thin to count (1 gm) — shown, adds nothing
• vs them: averages 12.0 over 4 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.