• 3.7 baseline — 0.6 × season 3.7 (10 gm) + 0.4 × last 10 3.7
• −0.1 opponent leak — they concede 35.2/game vs a 35.7 league average
• +1.1 at this ground — averages 4.8 there (77 gm)
• vs them: averages 3.1 over 9 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.