ReactiveTable.publish not return Expected data to client side

[Akhileshkumarr]

I want to return a collection having tracking number with trackingNumber.substr(0, 2); , if i 'console' this on server side it gives as expected result but if i returned then in client side return value is not coming as expected (trackingNumber.substr(0, 2)) , it returns without any changes (just as trackingNumber)
ReactiveTable.publish(
"OverallPackages", Packages, function() {
let packages = Packages.find({ trackingNumber : '7208457174' }).fetch();
packages.map((obj) => {
obj.trackingNumber = obj.trackingNumber.substr(0, 2);
console.log(obj); // result as expected (72)
return obj; // not return as expected (7208457174)
});
@here client side subscibe is--
return {
rowsPerPage: 20,
showColumnToggles: true,
showRowCount:true,
showFilter:true,
collection:"OverallPackages"}
Any idea to troubleshoot this ? help please
thanx