• 8.4 baseline — 0.6 × season 8.7 (18 gm) + 0.4 × last 10 8.0
• −0.6 opponent leak — they concede 145.2/game vs a 155.4 league average
• −2.4 at this ground — averages 6 there (9 gm)
• vs them: averages 9.0 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.