• 13.5 baseline — 0.6 × season 13.6 (13 gm) + 0.4 × last 10 13.4
• −0.1 opponent leak — they concede 153.7/game vs a 155.4 league average
• −4.8 at this ground — averages 8.8 there (56 gm)
• vs them: averages 8.3 over 7 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.