• 3.5 baseline — 0.6 × season 3.6 (11 gm) + 0.4 × last 10 3.2
• +0.3 opponent leak — they concede 25.8/game vs a 23.7 league average
• −1.9 at this ground — averages 1.6 there (5 gm)
• −0.5 wet forecast — averages 3 in the wet (8 gm)
• vs them: averages 2.4 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.