• 9.7 baseline — 0.6 × season 10.1 (7 gm) + 0.4 × last 10 9.1
• +0.3 opponent leak — they concede 219.6/game vs a 213.6 league average
• −2.8 at this ground — averages 6.9 there (11 gm)
• vs them: averages 8.0 over 2 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 21: 19 — far outside his usual range; kept in the average, not smoothed away.