• 18.9 baseline — 0.6 × season 18.9 (8 gm) + 0.4 × last 8 18.9
• −0.3 opponent leak — they concede 1663.5/game vs a 1687.8 league average
• +7.9 at this ground — averages 26.8 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 9: 77 — far outside his usual range; kept in the average, not smoothed away.