• 5.6 baseline — 0.6 × season 5.5 (15 gm) + 0.4 × last 10 5.9
• +0.3 opponent leak — they concede 164.6/game vs a 155.4 league average
• −1.9 at this ground — averages 3.7 there (19 gm)
• vs them: averages 6.2 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 21: 10 — far outside his usual range; kept in the average, not smoothed away.