• 15.9 baseline — 0.6 × season 16.1 (9 gm) + 0.4 × last 10 15.6
• −0.1 opponent leak — they concede 365.8/game vs a 369 league average
• wet forecast: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 15.8 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.