• 4.1 baseline — 0.6 × season 4.1 (20 gm) + 0.4 × last 10 4.1
• −0.3 opponent leak — they concede 145.2/game vs a 155.4 league average
• −1.1 at this ground — averages 3 there (4 gm)
• vs them: averages 3.5 over 4 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.