• 8.8 baseline — 0.6 × season 8.8 (18 gm) + 0.4 × last 10 8.9
• −0.3 opponent leak — they concede 357.8/game vs a 369 league average
• +1.5 at this ground — averages 10.4 there (59 gm)
• vs them: averages 10.8 over 6 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 15: 18 — far outside his usual range; kept in the average, not smoothed away.