• 0.1 baseline — 0.6 × season 0.2 (17 gm) + 0.4 × last 10 0.0
• +0.0 opponent leak — they concede 6.5/game vs a 5.1 league average
• +0.2 at this ground — averages 0.3 there (10 gm)
• +0.2 wet forecast — averages 0.3 in the wet (6 gm)
• vs them: averages 0.3 over 6 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.