• 2.2 baseline — 0.6 × season 2.3 (15 gm) + 0.4 × last 10 2.2
• +0.2 opponent leak — they concede 61.9/game vs a 56.6 league average
• −0.3 at this ground — averages 2 there (25 gm)
• vs them: averages 2.8 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.