• 11.1 baseline — 0.6 × season 11.3 (16 gm) + 0.4 × last 10 10.8
• +1.0 opponent leak — they concede 233.1/game vs a 213.6 league average
• +0.1 at this ground — averages 11.3 there (48 gm)
• −0.8 wet forecast — averages 10.3 in the wet (13 gm)
• vs them: averages 9.8 over 10 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.