• 0.2 baseline — 0.6 × season 0.2 (17 gm) + 0.4 × last 10 0.2
• +0.1 opponent leak — they concede 12.3/game vs a 9.4 league average
• −0.0 at this ground — averages 0.1 there (41 gm)
• −0.2 wet forecast — averages 0 in the wet (7 gm)
• vs them: averages 0.0 over 6 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.