Found this but this is not a good way https://github.com/osTicket/osTicket/issues/4189
Found the script which gets the json but I don't know from where is comming that json
<script>
$.drawPlots({"times":[1549324800,1549411200,1550102400],"plots":{"created":[1,5,1],"closed":[0,0,2],"reopened":[0,0,1],"overdue":[0,0,6]},"events":["created","closed","reopened","overdue"]});
</script>
also played with this files (dashboard.inc.php, dashboard.inc.js) but still didn't get the result