• 11.7 baseline — 0.6 × season 11.6 (9 gm) + 0.4 × last 10 11.9
• −0.2 opponent leak — they concede 363.9/game vs a 369 league average
• −0.6 at this ground — averages 11.1 there (9 gm)
• −0.2 wet forecast — averages 11.5 in the wet (4 gm)
• vs them: averages 10.4 over 5 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.