• 14.2 baseline — 0.6 × season 14.3 (18 gm) + 0.4 × last 10 14.0
• −0.3 opponent leak — they concede 209.2/game vs a 213.6 league average
• −0.6 at this ground — averages 13.6 there (16 gm)
• −0.6 wet forecast — averages 13.6 in the wet (8 gm)
• vs them: averages 10.7 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.