• 122.9 baseline — 0.6 × season 126.3 (14 gm) + 0.4 × last 10 117.8
• +2.1 opponent leak — they concede 1715.2/game vs a 1686.6 league average
• +1.8 at this ground — averages 124.7 there (6 gm)
• −9.5 wet forecast — averages 113.4 in the wet (7 gm)
• vs them: averages 135.9 over 9 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.