• 1.5 baseline — 0.6 × season 1.5 (20 gm) + 0.4 × last 10 1.5
• −0.0 opponent leak — they concede 55.5/game vs a 56.6 league average
• −0.1 at this ground — averages 1.4 there (22 gm)
• vs them: averages 2.5 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.