• 9.2 baseline — 0.6 × season 9.7 (19 gm) + 0.4 × last 10 8.3
• −0.0 opponent leak — they concede 367.1/game vs a 369 league average
• +0.7 at this ground — averages 9.9 there (18 gm)
• vs them: averages 13.5 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 19: 2 — far outside his usual range; kept in the average, not smoothed away.