• 2.7 baseline — 0.6 × season 2.8 (16 gm) + 0.4 × last 10 2.7
• +0.3 opponent leak — they concede 61.9/game vs a 56.6 league average
• +0.6 at this ground — averages 3.4 there (8 gm)
• vs them: averages 4.0 over 4 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.