• 1.8 baseline — 0.6 × season 1.8 (14 gm) + 0.4 × last 10 1.8
• +0.1 opponent leak — they concede 10/game vs a 9.7 league average
• −0.1 at this ground — averages 1.7 there (55 gm)
• −0.5 wet forecast — averages 1.3 in the wet (12 gm)
• vs them: averages 0.7 over 10 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.