• 8.3 baseline — 0.6 × season 9.2 (5 gm) + 0.4 × last 10 6.9
• +0.4 opponent leak — they concede 386.5/game vs a 369 league average
• +1.7 at this ground — averages 9.9 there (17 gm)
• vs them: averages 6.0 over 1 game — 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 6: 15 — far outside his usual range; kept in the average, not smoothed away.