• 4.6 baseline — 0.6 × season 5.0 (5 gm) + 0.4 × last 10 3.9
• +0.0 opponent leak — they concede 156.4/game vs a 155.4 league average
• +0.3 at this ground — averages 4.9 there (17 gm)
• vs them: averages 4.0 over 1 game — 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 19: 0 — far outside his usual range; kept in the average, not smoothed away.