Time Machine backup files in NAS drives show up as .Sparsebundle folders in Windows. If you want them excluded from your backup you can do so by performing the following steps:
- Right-click on your profile and select Modify
- At Simple settings page, click on Change Filter button
- At the Filters window, click on Add button under Files/folders NOT to copy
- Enter *\*.sparsebundle\ in the Filters dialog box that pops up and click OK.