• 3.6 baseline — 0.6 × season 3.6 (20 gm) + 0.4 × last 10 3.6
• −0.2 opponent leak — they concede 33.5/game vs a 35.7 league average
• +0.3 at this ground — averages 3.9 there (9 gm)
• vs them: averages 4.4 over 11 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 19: 9 — far outside his usual range; kept in the average, not smoothed away.