• 3.2 baseline — 0.6 × season 2.8 (15 gm) + 0.4 × last 10 3.8
• −1.2 opponent leak — they concede 15.1/game vs a 23.6 league average
• −0.8 at this ground — averages 2.4 there (37 gm)
• vs them: averages 1.8 over 9 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 16: 14 — far outside his usual range; kept in the average, not smoothed away.