• 39.9 baseline — 0.6 × season 40.6 (19 gm) + 0.4 × last 10 39.0
• −3.1 opponent leak — they concede 503.2/game vs a 545.7 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• vs them: averages 42.9 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.