• 19.1 baseline — 0.6 × season 19.8 (18 gm) + 0.4 × last 10 18.0
• −0.2 opponent leak — they concede 211.7/game vs a 213.6 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• −2.6 wet forecast — averages 16.5 in the wet (6 gm)
• vs them: averages 15.5 over 2 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.