• 2.5 baseline — 0.6 × season 2.5 (20 gm) + 0.4 × last 10 2.5
• −0.1 opponent leak — they concede 89.3/game vs a 93.4 league average
• −0.9 at this ground — averages 1.6 there (25 gm)
• vs them: averages 2.0 over 3 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.