• 0.5 baseline — 0.6 × season 0.5 (18 gm) + 0.4 × last 10 0.5
• −0.0 opponent leak — they concede 3.5/game vs a 3.9 league average
• −0.2 at this ground — averages 0.3 there (32 gm)
• −0.5 wet forecast — averages 0 in the wet (12 gm)
• vs them: averages 0.2 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.