• 2.9 baseline — 0.6 × season 3.8 (4 gm) + 0.4 × last 10 1.6
• +0.1 opponent leak — they concede 36.6/game vs a 35.7 league average
• −1.6 at this ground — averages 1.3 there (4 gm)
• vs them: averages 1.2 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.