• 15.9 baseline — 0.6 × season 16.3 (16 gm) + 0.4 × last 10 15.2
• +0.0 opponent leak — they concede 369.9/game vs a 369 league average
• +3.9 at this ground — averages 19.8 there (8 gm)
• vs them: averages 21.5 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 6: 27 — far outside his usual range; kept in the average, not smoothed away.