• 2.9 baseline — 0.6 × season 3.0 (20 gm) + 0.4 × last 10 2.8
• −0.2 opponent leak — they concede 32.7/game vs a 35.7 league average
• +1.1 at this ground — averages 4.1 there (69 gm)
• vs them: averages 2.7 over 10 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.