• 4.5 baseline — 0.6 × season 4.5 (11 gm) + 0.4 × last 10 4.5
• +0.2 opponent leak — they concede 196/game vs a 186.3 league average
• +1.1 at this ground — averages 5.6 there (31 gm)
• vs them: averages 6.1 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.