• 8.7 baseline — 0.6 × season 8.5 (20 gm) + 0.4 × last 10 8.9
• +0.2 opponent leak — they concede 158.8/game vs a 155.4 league average
• −1.2 at this ground — averages 7.5 there (4 gm)
• vs them: averages 13.0 over 1 game — evidence, never summed

Most signals here point under while you're on the over — worth reading the working above before you commit.

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.