• 13.0 baseline — 0.6 × season 12.9 (14 gm) + 0.4 × last 10 13.1
• −0.4 opponent leak — they concede 333/game vs a 344.7 league average
• −3.1 at this ground — averages 9.9 there (38 gm)
• vs them: averages 7.5 over 4 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 8: 27 — far outside his usual range; kept in the average, not smoothed away.