• 1.7 baseline — 0.6 × season 1.6 (13 gm) + 0.4 × last 10 1.8
• +0.2 opponent leak — they concede 64.3/game vs a 56.6 league average
• −0.2 at this ground — averages 1.5 there (4 gm)
• +0.3 wet forecast — averages 2 in the wet (18 gm)
• vs them: averages 2.0 over 8 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. Round 19: 4 — far outside his usual range; kept in the average, not smoothed away.