• 17.5 baseline — 0.6 × season 17.4 (9 gm) + 0.4 × last 10 17.5
• +0.4 opponent leak — they concede 377.9/game vs a 369 league average
• −1.2 at this ground — averages 16.3 there (21 gm)
• vs them: averages 20.3 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 6: 26 — far outside his usual range; kept in the average, not smoothed away.