• 4.1 baseline — 0.6 × season 3.8 (18 gm) + 0.4 × last 10 4.5
• −0.4 opponent leak — they concede 494.6/game vs a 544.6 league average
• −0.7 at this ground — averages 3.3 there (47 gm)
• vs them: averages 1.8 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 14: 13 — far outside his usual range; kept in the average, not smoothed away.