• 4.2 baseline — 0.6 × season 4.2 (20 gm) + 0.4 × last 10 4.3
• −0.3 opponent leak — they concede 145.2/game vs a 155.4 league average
• −0.3 at this ground — averages 3.9 there (32 gm)
• vs them: averages 4.0 over 1 game — 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. Round 2: 12 — far outside his usual range; kept in the average, not smoothed away.