• 12.6 baseline — 0.6 × season 12.1 (20 gm) + 0.4 × last 10 13.4
• −0.9 opponent leak — they concede 343.2/game vs a 369 league average
• −2.7 at this ground — averages 9.9 there (46 gm)
• vs them: averages 11.7 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 17: 24 — far outside his usual range; kept in the average, not smoothed away.