• 2.9 baseline — 0.6 × season 3.2 (19 gm) + 0.4 × last 10 2.6
• −0.2 opponent leak — they concede 87/game vs a 93.4 league average
• +0.6 at this ground — averages 3.5 there (8 gm)
• wet forecast: too thin to count (1 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.