• 0.8 baseline — 0.6 × season 0.8 (15 gm) + 0.4 × last 10 0.8
• +0.1 opponent leak — they concede 25.8/game vs a 23.7 league average
• +2.4 at this ground — averages 3.2 there (5 gm)
• −0.4 wet forecast — averages 0.4 in the wet (9 gm)
• vs them: averages 1.8 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.