• 2.2 baseline — 0.6 × season 2.1 (20 gm) + 0.4 × last 10 2.2
• −0.2 opponent leak — they concede 11.7/game vs a 12.8 league average
• −0.3 at this ground — averages 1.9 there (61 gm)
• vs them: averages 0.6 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.