• 5.5 baseline — 0.6 × season 5.5 (11 gm) + 0.4 × last 10 5.6
• +0.5 opponent leak — they concede 101.3/game vs a 93.4 league average
• −1.0 at this ground — averages 4.5 there (24 gm)
• vs them: averages 5.6 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.