• 31.8 baseline — 0.6 × season 31.7 (19 gm) + 0.4 × last 10 31.9
• +0.1 opponent leak — they concede 345.7/game vs a 344.9 league average
• −16.1 at this ground — averages 15.7 there (15 gm)
• −19.1 wet forecast — averages 12.8 in the wet (8 gm)
• vs them: averages 30.5 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.