• 6.7 baseline — 0.6 × season 6.7 (20 gm) + 0.4 × last 10 6.7
• +0.4 opponent leak — they concede 225.5/game vs a 213.6 league average
• +1.7 at this ground — averages 8.4 there (51 gm)
• vs them: averages 8.6 over 5 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 20: 15 — far outside his usual range; kept in the average, not smoothed away.