• 6.9 baseline — 0.6 × season 7.1 (20 gm) + 0.4 × last 10 6.6
• −0.1 opponent leak — they concede 209.4/game vs a 213.6 league average
• −0.3 at this ground — averages 6.6 there (53 gm)
• vs them: averages 4.8 over 6 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 15: 13 — far outside his usual range; kept in the average, not smoothed away.