• 3.2 baseline — 0.6 × season 3.5 (15 gm) + 0.4 × last 10 2.8
• −0.4 opponent leak — they concede 80.8/game vs a 93.4 league average
• −0.3 at this ground — averages 2.9 there (9 gm)
• −0.6 wet forecast — averages 2.6 in the wet (14 gm)
• vs them: averages 3.8 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.