• 1.9 baseline — 0.6 × season 1.5 (18 gm) + 0.4 × last 10 2.5
• −0.1 opponent leak — they concede 33.1/game vs a 35.3 league average
• −0.6 at this ground — averages 1.3 there (42 gm)
• vs them: averages 1.1 over 8 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.