• 1.0 baseline — 0.6 × season 1.0 (19 gm) + 0.4 × last 10 1.1
• +0.2 opponent leak — they concede 14.4/game vs a 12.3 league average
• +0.4 at this ground — averages 1.5 there (53 gm)
• +0.6 wet forecast — averages 1.7 in the wet (9 gm)
• vs them: averages 2.3 over 7 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.