• 15.8 baseline — 0.6 × season 16.1 (16 gm) + 0.4 × last 10 15.3
• +1.2 opponent leak — they concede 230.1/game vs a 213.6 league average
• −1.0 at this ground — averages 14.8 there (41 gm)
• vs them: averages 15.3 over 6 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 20: 1 — far outside his usual range; kept in the average, not smoothed away.