• 0.8 baseline — 0.6 × season 0.8 (20 gm) + 0.4 × last 10 0.8
• −0.0 opponent leak — they concede 33.9/game vs a 35.7 league average
• +0.4 at this ground — averages 1.2 there (38 gm)
• vs them: averages 0.8 over 8 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: 4 — far outside his usual range; kept in the average, not smoothed away.