• 2.3 baseline — 0.6 × season 2.4 (17 gm) + 0.4 × last 10 2.1
• −0.3 opponent leak — they concede 49/game vs a 56.6 league average
• −0.3 at this ground — averages 2 there (23 gm)
• vs them: averages 2.0 over 2 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.