curl -X POST "https://api-meter.metrifox.com/usage/events/adjust" \
  -H "x-api-key: your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "customer_key": "cust-6d11ca90",
    "event_id": "evt_12345",
    "actual_quantity": 4
  }'

{
  "data": {
    "event_id": "evt_12345",
    "adjusted": true,
    "actual_quantity": 4,
    "actual_credit_used": 0,
    "refunded_quantity": 1,
    "refunded_credit": 0,
    "deducted_quantity": 0,
    "deducted_credit": 0,
    "message": "Usage adjusted"
  }
}