Hi Praveen,
One Option could be storing the values of Quantity in the table in a hidden column, so that you can use that while creating the XML.
The XML which you have mentioned above is correct from the MII point of view because MII list contains the value along with the data type. That is why you are getting the values like this: [string:305].
For the work around, save Quantity values as comma separated String in String type of transaction property and then use String list to XML parser action block with Delimiter as ",".
Another work around could be Iterating on the List and then creating the XML document using SAP MII XML Output action blocks.
Regards,
Rohit Negi.