• 5.5 baseline — 0.6 × season 5.3 (14 gm) + 0.4 × last 10 5.7
• +0.4 opponent leak — they concede 38.4/game vs a 35.7 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• +1.8 wet forecast — averages 7.2 in the wet (14 gm)
• vs them: averages 6.1 over 7 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.