• 4.9 baseline — 0.6 × season 5.0 (11 gm) + 0.4 × last 10 4.7
• −0.1 opponent leak — they concede 211.2/game vs a 213.6 league average
• +1.4 at this ground — averages 6.3 there (10 gm)
• vs them: averages 6.3 over 3 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: 11 — far outside his usual range; kept in the average, not smoothed away.