• 0.6 baseline — 0.6 × season 0.7 (7 gm) + 0.4 × last 10 0.5
• −0.1 opponent leak — they concede 9.7/game vs a 12.2 league average
• −0.1 at this ground — averages 0.5 there (10 gm)
• vs them: averages 0.0 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 1: 3 — far outside his usual range; kept in the average, not smoothed away.