• 4.4 baseline — 0.6 × season 4.3 (20 gm) + 0.4 × last 10 4.7
• +0.4 opponent leak — they concede 61.9/game vs a 56.6 league average
• +1.4 at this ground — averages 5.8 there (10 gm)
• vs them: averages 5.4 over 11 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.