• 5.2 baseline — his last 10 games; only 3 this season, too few to blend
• +0.3 opponent leak — they concede 224.7/game vs a 213.6 league average
• +3.1 at this ground — averages 8.3 there (55 gm)
• +6.3 wet forecast — averages 11.5 in the wet (6 gm)
• vs them: averages 6.5 over 4 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.