• 5.0 baseline — 0.6 × season 5.0 (11 gm) + 0.4 × last 10 5.1
• +0.4 opponent leak — they concede 166.4/game vs a 155.4 league average
• +0.1 at this ground — averages 5.2 there (46 gm)
• −1.9 wet forecast — averages 3.1 in the wet (11 gm)
• vs them: averages 3.7 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.