• 2.4 baseline — 0.6 × season 2.4 (10 gm) + 0.4 × last 10 2.4
• +0.3 opponent leak — they concede 27.1/game vs a 23.7 league average
• −1.7 at this ground — averages 0.7 there (18 gm)
• vs them: averages 1.6 over 5 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.