• 21.4 baseline — 0.6 × season 21.6 (20 gm) + 0.4 × last 10 21.0
• +0.4 opponent leak — they concede 375.7/game vs a 369 league average
• +1.9 at this ground — averages 23.2 there (28 gm)
• vs them: averages 18.7 over 3 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: 35 — far outside his usual range; kept in the average, not smoothed away.