• 0.5 baseline — 0.6 × season 0.5 (17 gm) + 0.4 × last 10 0.5
• +0.1 opponent leak — they concede 10.8/game vs a 9.7 league average
• −0.4 at this ground — averages 0.1 there (10 gm)
• vs them: averages 0.2 over 9 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 6: 2 — far outside his usual range; kept in the average, not smoothed away.