I was able to work it out. This displays the value 0 of both arrays. Thanks for your help @Colin!!
**Function Node:**
var m = {};
m.data=[];
m.labels=[];
var datatemp=[];
msg.payload.forEach(function(row) {
datatemp.push(parseFloat(row.DISK_SPACE_USED));
m.labels.push(row.CUSTOMER);
});
m.data.push(datatemp);
return {payload:[m.data,m.labels]};
**Donut Graph node:**
Label: {{msg.payload[1][0]}}
Value format: {{msg.payload[0][0][0]}}