• 11.8 baseline — 0.6 × season 11.3 (20 gm) + 0.4 × last 10 12.5
• −0.2 opponent leak — they concede 209.2/game vs a 213.6 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• +3.0 wet forecast — averages 14.8 in the wet (13 gm)
• vs them: averages 13.1 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.