• 5.2 baseline — 0.6 × season 5.8 (16 gm) + 0.4 × last 10 4.4
• −0.3 opponent leak — they concede 200.8/game vs a 213.6 league average
• +1.7 at this ground — averages 6.9 there (9 gm)
• vs them: averages 6.3 over 8 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.