• 16.1 baseline — 0.6 × season 16.2 (9 gm) + 0.4 × last 10 16.0
• −0.5 opponent leak — they concede 357.8/game vs a 369 league average
• +0.6 at this ground — averages 16.7 there (11 gm)
• −0.2 wet forecast — averages 15.9 in the wet (10 gm)
• vs them: averages 15.0 over 6 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.