• 57.6 baseline — 0.6 × season 56.6 (13 gm) + 0.4 × last 10 59.1
• +1.5 opponent leak — they concede 559.8/game vs a 545.7 league average
• −24.2 at this ground — averages 33.4 there (26 gm)
• −27.5 wet forecast — averages 30.1 in the wet (14 gm)
• vs them: averages 41.0 over 4 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.