• 2.3 baseline — 0.6 × season 2.3 (20 gm) + 0.4 × last 10 2.2
• +0.0 opponent leak — they concede 12.5/game vs a 12.2 league average
• −1.4 at this ground — averages 0.9 there (21 gm)
• vs them: averages 1.5 over 4 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.