• 6.4 baseline — 0.6 × season 6.3 (20 gm) + 0.4 × last 10 6.5
• +0.9 opponent leak — they concede 106.2/game vs a 93.4 league average
• −1.9 at this ground — averages 4.5 there (37 gm)
• vs them: averages 4.9 over 8 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.