• 5.2 baseline — 0.6 × season 5.3 (13 gm) + 0.4 × last 10 5.1
• +0.7 opponent leak — they concede 64.3/game vs a 56.6 league average
• −0.6 at this ground — averages 4.6 there (23 gm)
• vs them: averages 4.0 over 2 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: 11 — far outside his usual range; kept in the average, not smoothed away.