• 10.4 baseline — 0.6 × season 10.0 (13 gm) + 0.4 × last 10 11.0
• +0.5 opponent leak — they concede 224.7/game vs a 213.6 league average
• −2.1 at this ground — averages 8.3 there (27 gm)
• +0.4 wet forecast — averages 10.8 in the wet (5 gm)
• vs them: averages 12.0 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.