• 8.6 baseline — 0.6 × season 8.6 (8 gm) + 0.4 × last 10 8.5
• −0.1 opponent leak — they concede 365.8/game vs a 369 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• +3.9 wet forecast — averages 12.5 in the wet (6 gm)
• vs them: averages 11.3 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 2: 16 — far outside his usual range; kept in the average, not smoothed away.