your data is in JSON format, but like blackhornet said it is not a format that C3 array will understand.
You can load the LastData from AJAX into a C3 JSON object, and access the data by keys, and if you really wanted loop through that to load into an array.
to get it directly into an array, you would have to have the script on your server build a C3 compatible JSON file. BlackHornet was suggesting taking an Array from C3 and outputting it as JSON so you can see what it would have to look like.
here is code that worked fine for me:
Edit: should have refreshed first! :)