• 4.4 baseline — 0.6 × season 4.6 (19 gm) + 0.4 × last 10 4.0
• +0.6 opponent leak — they concede 106.2/game vs a 93.4 league average
• −1.6 at this ground — averages 2.8 there (26 gm)
• −2.1 wet forecast — averages 2.3 in the wet (4 gm)
• vs them: averages 5.0 over 2 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.