• 1.3 baseline — 0.6 × season 1.6 (18 gm) + 0.4 × last 10 0.8
• +0.1 opponent leak — they concede 25.8/game vs a 23.7 league average
• +1.1 at this ground — averages 2.4 there (5 gm)
• −1.3 wet forecast — averages 0 in the wet (5 gm)
• vs them: averages 1.5 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 9: 12 — far outside his usual range; kept in the average, not smoothed away.