• 11.2 baseline — 0.6 × season 11.9 (15 gm) + 0.4 × last 10 10.2
• +0.3 opponent leak — they concede 190.8/game vs a 185.9 league average
• +1.0 at this ground — averages 12.2 there (38 gm)
• +1.1 wet forecast — averages 12.4 in the wet (13 gm)
• vs them: averages 13.9 over 7 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.