• 13.1 baseline — 0.6 × season 13.1 (18 gm) + 0.4 × last 10 13.1
• +1.2 opponent leak — they concede 233.1/game vs a 213.6 league average
• −2.7 at this ground — averages 10.4 there (18 gm)
• vs them: averages 10.6 over 12 games — 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.