• 8.1 baseline — 0.6 × season 8.2 (14 gm) + 0.4 × last 10 7.9
• −0.2 opponent leak — they concede 207.8/game vs a 213.6 league average
• +0.7 at this ground — averages 8.8 there (75 gm)
• vs them: averages 8.1 over 7 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 1: 15 — far outside his usual range; kept in the average, not smoothed away.