• 13.0 baseline — 0.6 × season 13.3 (20 gm) + 0.4 × last 10 12.7
• +0.2 opponent leak — they concede 349.4/game vs a 344.9 league average
• −3.4 at this ground — averages 9.6 there (17 gm)
• vs them: averages 13.8 over 5 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.