• 1.3 baseline — 0.6 × season 1.3 (15 gm) + 0.4 × last 10 1.3
• −0.0 opponent leak — they concede 11.8/game vs a 12.2 league average
• +0.4 at this ground — averages 1.7 there (65 gm)
• vs them: averages 1.7 over 7 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 4: 5 — far outside his usual range; kept in the average, not smoothed away.