Capture partial value from JSON payload

[ravivish83]

In the JSON payload like below, I have to capture "severity": only '4' digit value but ExtractVariables gives Sev4 , and which 4 digit value needs to be sent to other JSON pay load via <Set> <Payload contentType="application/json" variablePrefix="@" variableSuffix="#">

{
  "schemaId": "azureMonitorCommonAlertSchema",
  "data": {
    "essentials": {
      "alertId": "/subscriptions/000000",
      "severity": "Sev4",
      ...
    }
    ...
  }
}

So is there a way to capture the partial value and save it to the parameter for passing to another JSON