• 8.0 baseline — 0.6 × season 7.4 (16 gm) + 0.4 × last 10 8.9
• +0.0 opponent leak — they concede 187.3/game vs a 186.3 league average
• −0.4 wet forecast — averages 7.6 in the wet (5 gm)
• vs them: averages 6.3 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.