• 0.9 baseline — 0.6 × season 0.9 (19 gm) + 0.4 × last 10 0.8
• −0.0 opponent leak — they concede 34.2/game vs a 35.7 league average
• +0.1 at this ground — averages 1 there (52 gm)
• vs them: averages 2.2 over 6 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.