• 6.4 baseline — 0.6 × season 6.4 (10 gm) + 0.4 × last 10 6.4
• +0.4 opponent leak — they concede 368.1/game vs a 344.7 league average
• −0.4 at this ground — averages 6 there (23 gm)
• vs them: averages 5.7 over 3 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.