• 3.6 baseline — 0.6 × season 3.9 (14 gm) + 0.4 × last 10 3.2
• +0.4 opponent leak — they concede 104/game vs a 93.4 league average
• +1.1 at this ground — averages 4.7 there (62 gm)
• vs them: averages 5.0 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.