You are needing to upload data from Excel that has leading spaces in your field. When it is placed in SAP from Winshuttle, the spaces are removed. Using the "Pre-padding" setting is not an option as the values will not always be the same length.
Studio 11 contains a setting that will automatically trim leading spaces in your data. If this is not needed you can navigate to the Options screen > Data Settings > and uncheck "Trim leading" and "Trim trailing" spaces.