• 4.1 baseline — 0.6 × season 4.2 (11 gm) + 0.4 × last 10 3.9
• −0.3 opponent leak — they concede 87/game vs a 93.4 league average
• −0.7 at this ground — averages 3.4 there (10 gm)
• vs them: averages 1.0 over 2 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.