• 3.3 baseline — 0.6 × season 3.4 (19 gm) + 0.4 × last 10 3.0
• +0.1 opponent leak — they concede 158.8/game vs a 155.4 league average
• +0.4 at this ground — averages 3.6 there (62 gm)
• vs them: averages 2.8 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.