• 0.9 baseline — 0.6 × season 1.0 (18 gm) + 0.4 × last 10 0.7
• +0.1 opponent leak — they concede 37.8/game vs a 35.7 league average
• +0.4 at this ground — averages 1.3 there (16 gm)
• vs them: averages 0.0 over 3 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.