• 13.6 baseline — 0.6 × season 13.6 (13 gm) + 0.4 × last 10 13.7
• +1.1 opponent leak — they concede 399.5/game vs a 369 league average
• +1.1 at this ground — averages 14.8 there (18 gm)
• vs them: averages 14.8 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 8: 22 — far outside his usual range; kept in the average, not smoothed away.