• 0.5 baseline — 0.6 × season 0.5 (15 gm) + 0.4 × last 10 0.5
• −0.1 opponent leak — they concede 4.5/game vs a 5.1 league average
• +0.7 at this ground — averages 1.3 there (4 gm)
• vs them: averages 1.2 over 6 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 20: 2 — far outside his usual range; kept in the average, not smoothed away.