• 0.5 baseline — 0.6 × season 0.5 (8 gm) + 0.4 × last 8 0.5
• −0.1 opponent leak — they concede 7.8/game vs a 9.4 league average
• −0.3 at this ground — averages 0.3 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: 2 — far outside his usual range; kept in the average, not smoothed away.