• 5.5 baseline — 0.6 × season 5.8 (16 gm) + 0.4 × last 10 5.0
• +0.1 opponent leak — they concede 157.2/game vs a 155.4 league average
• +1.9 at this ground — averages 7.4 there (8 gm)
• vs them: averages 8.8 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.