• 60.8 baseline — 0.6 × season 64.7 (20 gm) + 0.4 × last 10 55.0
• −4.0 opponent leak — they concede 1576.6/game vs a 1687.8 league average
• +21.7 at this ground — averages 82.5 there (4 gm)
• vs them: averages 63.9 over 8 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 4: 152 — far outside his usual range; kept in the average, not smoothed away.