• 1.0 baseline — 0.6 × season 1.1 (17 gm) + 0.4 × last 10 1.0
• −0.1 opponent leak — they concede 33.1/game vs a 35.7 league average
• +0.5 at this ground — averages 1.5 there (4 gm)
• vs them: averages 2.0 over 4 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 4: 4 — far outside his usual range; kept in the average, not smoothed away.