• 11.8 baseline — 0.6 × season 11.2 (6 gm) + 0.4 × last 10 12.7
• +0.6 opponent leak — they concede 224.7/game vs a 213.6 league average
• +0.3 at this ground — averages 12.1 there (34 gm)
• +0.6 wet forecast — averages 12.3 in the wet (6 gm)
• vs them: averages 14.0 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.