• 0.9 baseline — 0.6 × season 0.8 (20 gm) + 0.4 × last 10 1.1
• −0.0 opponent leak — they concede 9.3/game vs a 9.7 league average
• −0.0 at this ground — averages 0.9 there (17 gm)
• vs them: averages 0.7 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 20: 3 — far outside his usual range; kept in the average, not smoothed away.