• 0.3 baseline — 0.6 × season 0.4 (16 gm) + 0.4 × last 10 0.3
• +0.0 opponent leak — they concede 10.2/game vs a 9.7 league average
• +0.1 at this ground — averages 0.5 there (17 gm)
• +0.3 wet forecast — averages 0.6 in the wet (5 gm)
• vs them: averages 1.0 over 1 game — 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.