• 8.9 baseline — his last 10 games; only 2 this season, too few to blend
• −0.1 opponent leak — they concede 365.8/game vs a 369 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• wet forecast: too thin to count (1 gm) — shown, adds nothing
• vs them: averages 9.0 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.