• 1.6 baseline — 0.6 × season 1.4 (17 gm) + 0.4 × last 10 1.9
• −0.2 opponent leak — they concede 50.6/game vs a 56.6 league average
• −0.1 at this ground — averages 1.6 there (20 gm)
• vs them: averages 0.9 over 12 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 11: 6 — far outside his usual range; kept in the average, not smoothed away.