• 3.7 baseline — 0.6 × season 3.9 (19 gm) + 0.4 × last 10 3.3
• +0.5 opponent leak — they concede 106.2/game vs a 93.4 league average
• −0.7 at this ground — averages 2.9 there (36 gm)
• −1.0 wet forecast — averages 2.7 in the wet (15 gm)
• vs them: averages 4.6 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 9: 9 — far outside his usual range; kept in the average, not smoothed away.