• 9.3 baseline — 0.6 × season 9.3 (18 gm) + 0.4 × last 10 9.3
• +0.2 opponent leak — they concede 219.2/game vs a 213.6 league average
• +0.5 at this ground — averages 9.9 there (42 gm)
• vs them: averages 10.4 over 8 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 19: 0 — far outside his usual range; kept in the average, not smoothed away.