void myHandler(const char *event, const char *data) {
// Handle the integration response
}
you get data from the event, so you need to process that into usable data.
One way would be to add a Response Template (mustache template) to your Integration/WebHook and get just deal with the numbers(if that is all you are really interested in).
Another approach would to be to use the JSON parser library (a couple available if you search this site) to extract the values from the JSON object you received in data.