• 14.8 baseline — 0.6 × season 14.3 (6 gm) + 0.4 × last 10 15.6
• −0.8 opponent leak — they concede 201.8/game vs a 213.6 league average
• +0.2 at this ground — averages 15.1 there (67 gm)
• vs them: averages 13.0 over 9 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 21: 5 — far outside his usual range; kept in the average, not smoothed away.