• 3.0 baseline — 0.6 × season 3.0 (20 gm) + 0.4 × last 10 3.1
• +0.4 opponent leak — they concede 64.2/game vs a 56.6 league average
• −0.5 at this ground — averages 2.6 there (34 gm)
• vs them: averages 4.2 over 6 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.