• 0.6 baseline — 0.6 × season 0.5 (16 gm) + 0.4 × last 10 0.7
• +0.2 opponent leak — they concede 12.3/game vs a 9.4 league average
• +0.1 at this ground — averages 0.7 there (48 gm)
• +0.3 wet forecast — averages 0.8 in the wet (13 gm)
• vs them: averages 0.5 over 10 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: 4 — far outside his usual range; kept in the average, not smoothed away.