• 29.9 baseline — 0.6 × season 29.3 (14 gm) + 0.4 × last 10 30.7
• +4.1 opponent leak — they concede 618.4/game vs a 544.2 league average
• +0.1 at this ground — averages 30 there (38 gm)
• vs them: averages 35.8 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.