• 1.0 baseline — 0.6 × season 1.0 (12 gm) + 0.4 × last 10 0.9
• +0.3 opponent leak — they concede 12.3/game vs a 9.4 league average
• +0.2 at this ground — averages 1.1 there (58 gm)
• −0.4 wet forecast — averages 0.6 in the wet (14 gm)
• vs them: averages 1.1 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 19: 4 — far outside his usual range; kept in the average, not smoothed away.