• 6.8 baseline — 0.6 × season 6.5 (20 gm) + 0.4 × last 10 7.3
• +0.5 opponent leak — they concede 100.5/game vs a 93.4 league average
• −1.3 at this ground — averages 5.5 there (4 gm)
• vs them: averages 8.5 over 2 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: 13 — far outside his usual range; kept in the average, not smoothed away.