• 11.8 baseline — 0.6 × season 10.5 (20 gm) + 0.4 × last 10 13.7
• −1.5 opponent leak — they concede 475.8/game vs a 544.6 league average
• +1.3 at this ground — averages 13.1 there (10 gm)
• vs them: averages 2.0 over 3 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: 32 — far outside his usual range; kept in the average, not smoothed away.