• 6.3 baseline — 0.6 × season 6.1 (20 gm) + 0.4 × last 10 6.6
• +0.7 opponent leak — they concede 104/game vs a 93.4 league average
• +0.9 at this ground — averages 7.2 there (79 gm)
• vs them: averages 8.8 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.