Using a third-party NAS as a Time Machine backup destination is unsupported by Apple. Search this site for reports of the resulting data-loss catastrophes. If such a catastrophe happens to you, your only recourse will be to the NAS vendor. Neither Apple nor anyone here will be able to help you.
If you intend to use a third-party NAS with Time Machine, you must verify that the device meets the Time Machine Network Interface Specification (TMNIS).