• 16.1 baseline — 0.6 × season 15.7 (15 gm) + 0.4 × last 10 16.7
• +0.9 opponent leak — they concede 225.5/game vs a 213.6 league average
• −0.5 at this ground — averages 15.6 there (42 gm)
• vs them: averages 13.7 over 10 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 18: 5 — far outside his usual range; kept in the average, not smoothed away.