• 15.7 baseline — 0.6 × season 16.9 (20 gm) + 0.4 × last 10 14.0
• −1.1 opponent leak — they concede 343.2/game vs a 369 league average
• −1.5 at this ground — averages 14.3 there (4 gm)
• vs them: averages 15.0 over 5 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 3: 31 — far outside his usual range; kept in the average, not smoothed away.