• 0.4 baseline — 0.6 × season 0.3 (18 gm) + 0.4 × last 10 0.4
• +0.0 opponent leak — they concede 10.2/game vs a 9.4 league average
• +0.1 at this ground — averages 0.5 there (20 gm)
• vs them: averages 0.3 over 3 games — evidence, never summed

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 18: 2 — far outside his usual range; kept in the average, not smoothed away.