• 6.0 baseline — 0.6 × season 6.0 (8 gm) + 0.4 × last 10 5.9
• −0.2 opponent leak — they concede 207.8/game vs a 213.6 league average
• +0.8 at this ground — averages 6.7 there (21 gm)
• vs them: averages 8.4 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.