• 2.1 baseline — 0.6 × season 2.2 (19 gm) + 0.4 × last 10 1.9
• +0.0 opponent leak — they concede 12.8/game vs a 12.8 league average
• +0.0 at this ground — averages 2.1 there (78 gm)
• vs them: averages 1.3 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 1: 6 — far outside his usual range; kept in the average, not smoothed away.