• 1.0 baseline — 0.6 × season 1.0 (11 gm) + 0.4 × last 10 0.9
• +0.1 opponent leak — they concede 38.8/game vs a 35.7 league average
• +1.0 wet forecast — averages 2 in the wet (6 gm)
• vs them: averages 1.9 over 8 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.