• 15.7 baseline — 0.6 × season 16.9 (20 gm) + 0.4 × last 10 14.0
• +0.9 opponent leak — they concede 389.2/game vs a 369 league average
• −1.8 at this ground — averages 13.9 there (51 gm)
• −3.2 wet forecast — averages 12.5 in the wet (8 gm)
• vs them: averages 12.4 over 5 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 3: 31 — far outside his usual range; kept in the average, not smoothed away.