• 1.0 baseline — 0.6 × season 1.1 (20 gm) + 0.4 × last 10 1.0
• +0.1 opponent leak — they concede 61.9/game vs a 56.6 league average
• −0.8 at this ground — averages 0.3 there (4 gm)
• vs them: averages 0.8 over 5 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.