• 5.5 baseline — 0.6 × season 5.2 (18 gm) + 0.4 × last 10 5.9
• −0.2 opponent leak — they concede 34.1/game vs a 35.7 league average
• −1.7 at this ground — averages 3.8 there (16 gm)
• vs them: averages 3.4 over 12 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: 12 — far outside his usual range; kept in the average, not smoothed away.