• 0.6 baseline — 0.6 × season 0.9 (20 gm) + 0.4 × last 10 0.2
• −0.2 opponent leak — they concede 15.1/game vs a 23.7 league average
• +0.7 at this ground — averages 1.3 there (6 gm)
• vs them: averages 2.9 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: 8 — far outside his usual range; kept in the average, not smoothed away.