• 3.5 baseline — 0.6 × season 3.4 (20 gm) + 0.4 × last 10 3.6
• +0.4 opponent leak — they concede 13.5/game vs a 12.2 league average
• −1.9 at this ground — averages 1.6 there (9 gm)
• vs them: averages 2.0 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 6: 9 — far outside his usual range; kept in the average, not smoothed away.