• 0.2 baseline — 0.6 × season 0.2 (18 gm) + 0.4 × last 10 0.2
• −0.0 opponent leak — they concede 4/game vs a 4.1 league average
• at this ground: too thin to count (2 gm) — shown, adds nothing
• +0.3 wet forecast — averages 0.5 in the wet (10 gm)
• vs them: averages 0.8 over 6 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.