• 0.7 baseline — 0.6 × season 0.6 (15 gm) + 0.4 × last 10 0.8
• −0.1 opponent leak — they concede 8.7/game vs a 9.4 league average
• +0.8 at this ground — averages 1.5 there (4 gm)

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: 3 — far outside his usual range; kept in the average, not smoothed away.