• 3.8 baseline — 0.6 × season 3.5 (20 gm) + 0.4 × last 10 4.1
• +0.1 opponent leak — they concede 36.6/game vs a 35.7 league average
• −0.5 at this ground — averages 3.3 there (35 gm)
• vs them: averages 5.0 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 18: 10 — far outside his usual range; kept in the average, not smoothed away.