• 0.8 baseline — 0.6 × season 1.3 (16 gm) + 0.4 × last 10 0.2
• −0.1 opponent leak — they concede 30.1/game vs a 35.3 league average
• −0.5 at this ground — averages 0.3 there (10 gm)
• vs them: averages 0.5 over 4 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 4: 8 — far outside his usual range; kept in the average, not smoothed away.