• 10.9 baseline — 0.6 × season 11.0 (17 gm) + 0.4 × last 10 10.8
• +0.8 opponent leak — they concede 166.4/game vs a 155.4 league average
• −3.4 at this ground — averages 7.5 there (4 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 12: 23 — far outside his usual range; kept in the average, not smoothed away.