• 4.4 baseline — 0.6 × season 4.2 (16 gm) + 0.4 × last 10 4.8
• −0.2 opponent leak — they concede 89.3/game vs a 93.4 league average
• −0.2 at this ground — averages 4.2 there (36 gm)
• vs them: averages 1.5 over 2 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 20: 14 — far outside his usual range; kept in the average, not smoothed away.