Reproducing these numbers

curl -s -H "Authorization: Bearer $PIXELLAB_API_KEY" \
  https://api.pixellab.ai/v2/balance

The count lives at subscription.generations, not at the top level. A probe reading .generations gets undefined and silently reports every cost as NaN rather than failing:

{ "credits":      { "type": "usd", "usd": 0.0 },
  "subscription": { "type": "generations", "status": "active",
                    "plan": "Tier 2: Pixel Artisan",
                    "generations": 1281.0, "total": 5000.0 } }

Take a balance reading, make one call, wait a few seconds, read again. Prefer the response's usage field where present. It is inline, exact, and immune to the billing lag.