• 6.6 baseline — 0.6 × season 6.7 (11 gm) + 0.4 × last 10 6.3
• −0.1 opponent leak — they concede 152.1/game vs a 155.4 league average
• +2.3 wet forecast — averages 8.8 in the wet (6 gm)
• vs them: averages 7.5 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.