• 5.5 baseline — 0.6 × season 5.6 (19 gm) + 0.4 × last 10 5.3
• −0.3 opponent leak — they concede 88.8/game vs a 93.4 league average
• −1.2 wet forecast — averages 4.3 in the wet (4 gm)
• vs them: averages 5.8 over 4 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: 13 — far outside his usual range; kept in the average, not smoothed away.