• 6.0 baseline — 0.6 × season 5.5 (15 gm) + 0.4 × last 10 6.6
• +0.1 opponent leak — they concede 157.2/game vs a 155.4 league average
• +0.1 at this ground — averages 6.1 there (31 gm)
• vs them: averages 7.3 over 4 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.