• 148.7 baseline — 0.6 × season 150.2 (11 gm) + 0.4 × last 10 146.5
• +2.5 opponent leak — they concede 1715.2/game vs a 1686.6 league average
• +0.5 at this ground — averages 149.2 there (5 gm)
• −16.7 wet forecast — averages 132 in the wet (8 gm)
• vs them: averages 148.3 over 10 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.