• 3.7 baseline — 0.6 × season 3.6 (20 gm) + 0.4 × last 10 3.8
• −0.2 opponent leak — they concede 88.8/game vs a 93.4 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• −1.7 wet forecast — averages 2 in the wet (8 gm)
• vs them: averages 3.0 over 9 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.