• 6.1 baseline — 0.6 × season 6.2 (20 gm) + 0.4 × last 10 6.1
• −0.1 opponent leak — they concede 210.3/game vs a 213.6 league average
• +0.5 at this ground — averages 6.6 there (34 gm)
• vs them: averages 7.2 over 9 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.