• 31.1 baseline — 0.6 × season 30.7 (14 gm) + 0.4 × last 10 31.6
• +2.1 opponent leak — they concede 368.1/game vs a 344.7 league average
• +3.1 at this ground — averages 34.2 there (5 gm)
• vs them: averages 43.6 over 5 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.