• 2.6 baseline — 0.6 × season 2.8 (13 gm) + 0.4 × last 10 2.4
• −1.0 opponent leak — they concede 15.1/game vs a 23.7 league average
• −1.3 at this ground — averages 1.3 there (31 gm)
• vs them: averages 0.5 over 8 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: 16 — far outside his usual range; kept in the average, not smoothed away.