• 2.5 baseline — 0.6 × season 2.2 (20 gm) + 0.4 × last 10 2.9
• +0.2 opponent leak — they concede 38.4/game vs a 35.7 league average
• +1.0 at this ground — averages 3.5 there (10 gm)
• vs them: averages 3.0 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.