• 19.0 baseline — 0.6 × season 19.6 (20 gm) + 0.4 × last 10 18.1
• −0.1 opponent leak — they concede 154.7/game vs a 155.4 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• −2.0 wet forecast — averages 17 in the wet (13 gm)
• vs them: averages 17.6 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.