• 2.8 baseline — 0.6 × season 2.8 (9 gm) + 0.4 × last 10 2.9
• +0.0 opponent leak — they concede 157.2/game vs a 155.4 league average
• +0.8 at this ground — averages 3.6 there (31 gm)
• vs them: averages 3.8 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.