• 3.8 baseline — 0.6 × season 3.8 (12 gm) + 0.4 × last 10 3.8
• +0.3 opponent leak — they concede 38.8/game vs a 35.7 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• −0.0 wet forecast — averages 3.8 in the wet (9 gm)
• vs them: averages 4.9 over 8 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.