• 12.6 baseline — 0.6 × season 12.5 (19 gm) + 0.4 × last 10 12.8
• +0.3 opponent leak — they concede 378.4/game vs a 369 league average
• −2.3 at this ground — averages 10.3 there (33 gm)
• vs them: averages 6.7 over 3 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.