• 1.2 baseline — 0.6 × season 1.4 (17 gm) + 0.4 × last 10 0.8
• +0.2 opponent leak — they concede 27.1/game vs a 23.7 league average
• −0.2 at this ground — averages 1 there (4 gm)
• vs them: averages 2.7 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 2: 8 — far outside his usual range; kept in the average, not smoothed away.