• 0.9 baseline — 0.6 × season 0.9 (9 gm) + 0.4 × last 10 0.9
• +0.1 opponent leak — they concede 64.2/game vs a 56.6 league average
• +0.8 at this ground — averages 1.7 there (12 gm)
• +0.9 wet forecast — averages 1.8 in the wet (4 gm)
• vs them: averages 1.3 over 8 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: 3 — far outside his usual range; kept in the average, not smoothed away.