• 1.4 baseline — 0.6 × season 1.3 (20 gm) + 0.4 × last 10 1.7
• −0.2 opponent leak — they concede 50.3/game vs a 56.6 league average
• +0.1 at this ground — averages 1.5 there (16 gm)
• vs them: averages 0.0 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.