• 59.5 baseline — 0.6 × season 62.6 (12 gm) + 0.4 × last 10 55.0
• +1.0 opponent leak — they concede 1715.2/game vs a 1686.6 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• +12.3 wet forecast — averages 71.8 in the wet (5 gm)
• vs them: averages 70.0 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.