I guess the code you are using of for HTML 5 file system api. check this. this window.webkitStorageInfo.queryUsageAndQuota(webkitStorageInfo.TEMPORARY, console.log.bind(console))
also returns same as your code. you can calculate used localstorage
you can use something like this:
var _lsTotal=0,_xLen,_x;for(_x in localStorage){_xLen= ((localStorage[_x].length + _x.length)* 2);_lsTotal+=_xLen; console.log(_x.substr(0,50)+" = "+ (_xLen/1024).toFixed(2)+" KB")};console.log("Total = " + (_lsTotal / 1024).toFixed(2) + " KB");
Took it from here.
Chrome allows 5MB of data or 5101 k character as per this test so you can calculate the remaining storage.