• 5.6 baseline — 0.6 × season 5.8 (19 gm) + 0.4 × last 10 5.3
• +0.8 opponent leak — they concede 106.2/game vs a 93.4 league average
• −0.6 at this ground — averages 5 there (42 gm)
• −0.5 wet forecast — averages 5.2 in the wet (6 gm)
• vs them: averages 9.0 over 2 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.