• 0.2 baseline — 0.6 × season 0.2 (13 gm) + 0.4 × last 10 0.1
• −0.0 opponent leak — they concede 12.2/game vs a 12.8 league average
• +0.1 at this ground — averages 0.3 there (4 gm)
• +0.3 wet forecast — averages 0.4 in the wet (14 gm)
• vs them: averages 0.0 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.