• 12.7 baseline — 0.6 × season 12.4 (9 gm) + 0.4 × last 10 13.2
• −0.8 opponent leak — they concede 345.4/game vs a 369 league average
• +1.6 at this ground — averages 14.3 there (23 gm)
• vs them: averages 12.0 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 4: 24 — far outside his usual range; kept in the average, not smoothed away.