• 32.1 baseline — 0.6 × season 32.4 (9 gm) + 0.4 × last 10 31.7
• −4.1 opponent leak — they concede 475.8/game vs a 544.6 league average
• +6.5 at this ground — averages 38.6 there (5 gm)
• vs them: averages 56.8 over 4 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.