• 17.6 baseline — 0.6 × season 17.8 (12 gm) + 0.4 × last 10 17.3
• −0.2 opponent leak — they concede 365.8/game vs a 369 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• vs them: averages 15.8 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.