• 3.6 baseline — 0.6 × season 3.6 (18 gm) + 0.4 × last 10 3.6
• −1.3 opponent leak — they concede 15.1/game vs a 23.7 league average
• −0.9 at this ground — averages 2.7 there (34 gm)
• vs them: averages 0.0 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 4: 16 — far outside his usual range; kept in the average, not smoothed away.