• 31.6 baseline — 0.6 × season 31.4 (12 gm) + 0.4 × last 10 31.8
• +0.1 opponent leak — they concede 345.9/game vs a 344.9 league average
• −0.1 at this ground — averages 31.5 there (8 gm)
• vs them: averages 33.5 over 2 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.