• 19.6 baseline — 0.6 × season 19.6 (10 gm) + 0.4 × last 10 19.6
• −0.4 opponent leak — they concede 209.2/game vs a 213.6 league average
• −2.6 at this ground — averages 17 there (84 gm)
• vs them: averages 17.9 over 14 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 5: 7 — far outside his usual range; kept in the average, not smoothed away.