• 5.0 baseline — 0.6 × season 5.0 (8 gm) + 0.4 × last 10 4.9
• +0.8 opponent leak — they concede 108.9/game vs a 93.4 league average
• −1.1 at this ground — averages 3.8 there (46 gm)
• vs them: averages 3.9 over 7 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 3: 13 — far outside his usual range; kept in the average, not smoothed away.