• 3.1 baseline — 0.6 × season 3.1 (20 gm) + 0.4 × last 10 3.0
• −0.0 opponent leak — they concede 154.7/game vs a 155.4 league average
• +0.2 at this ground — averages 3.3 there (4 gm)
• +0.7 wet forecast — averages 3.8 in the wet (12 gm)
• vs them: averages 3.0 over 7 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 5: 8 — far outside his usual range; kept in the average, not smoothed away.