• 3.4 baseline — 0.6 × season 3.5 (14 gm) + 0.4 × last 10 3.3
• +0.2 opponent leak — they concede 37.8/game vs a 35.7 league average
• +0.5 at this ground — averages 3.9 there (31 gm)
• vs them: averages 3.9 over 7 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.