• 1.1 baseline — 0.6 × season 1.1 (20 gm) + 0.4 × last 10 1.0
• −0.1 opponent leak — they concede 51/game vs a 56.6 league average
• +0.4 at this ground — averages 1.4 there (77 gm)
• vs them: averages 1.2 over 9 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.