• 57.4 baseline — 0.6 × season 54.9 (20 gm) + 0.4 × last 10 61.1
• −0.3 opponent leak — they concede 1679.1/game vs a 1686.6 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• +21.1 wet forecast — averages 78.5 in the wet (11 gm)
• vs them: averages 66.8 over 10 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.