• 3.8 baseline — 0.6 × season 3.5 (15 gm) + 0.4 × last 10 4.3
• +0.5 opponent leak — they concede 64.2/game vs a 56.6 league average
• +0.7 at this ground — averages 4.5 there (8 gm)
• wet forecast: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 3.2 over 5 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.