• 2.2 baseline — 0.6 × season 2.0 (5 gm) + 0.4 × last 10 2.6
• −0.1 opponent leak — they concede 34.2/game vs a 35.7 league average
• +2.2 at this ground — averages 4.4 there (49 gm)
• vs them: averages 4.7 over 6 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.