• 3.6 baseline — 0.6 × season 3.9 (8 gm) + 0.4 × last 10 3.1
• −0.1 opponent leak — they concede 181.6/game vs a 185.9 league average
• −0.3 at this ground — averages 3.3 there (4 gm)
• vs them: averages 15.0 over 2 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.