• 4.1 baseline — 0.6 × season 3.7 (20 gm) + 0.4 × last 10 4.7
• +0.1 opponent leak — they concede 57.5/game vs a 56.6 league average
• −0.8 at this ground — averages 3.3 there (24 gm)
• vs them: averages 3.0 over 2 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 17: 9 — far outside his usual range; kept in the average, not smoothed away.