• 5.2 baseline — 0.6 × season 4.7 (21 gm) + 0.4 × last 10 6.0
• +0.3 opponent leak — they concede 368.1/game vs a 344.9 league average
• −1.9 at this ground — averages 3.3 there (19 gm)
• vs them: averages 2.0 over 2 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.