• 1.2 baseline — 0.6 × season 1.3 (4 gm) + 0.4 × last 10 1.2
• +0.1 opponent leak — they concede 36.5/game vs a 32.8 league average
• −0.2 at this ground — averages 1 there (26 gm)
• vs them: averages 0.5 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.