• 5.5 baseline — 0.6 × season 5.8 (18 gm) + 0.4 × last 10 5.2
• +0.0 opponent leak — they concede 94/game vs a 93.4 league average
• +0.4 at this ground — averages 5.9 there (10 gm)
• vs them: averages 5.9 over 9 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 1: 13 — far outside his usual range; kept in the average, not smoothed away.