• 10.6 baseline — 0.6 × season 10.3 (9 gm) + 0.4 × last 10 10.9
• +0.3 opponent leak — they concede 192.3/game vs a 186.3 league average
• +0.3 wet forecast — averages 10.9 in the wet (10 gm)
• vs them: averages 9.7 over 6 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.