Why Is My New SanDisk Ultra 128GB microSDXC only showing 119gb Full Memory Space

There might be two possible reasons either you make some files hidden and forgot or nay vrus attack. Simply check for hidden files fist. Or scan the sd card using any antivirus.  I also faced same situation in which my 64 GB sd card showing only 40 GB space. Then I scaned my sd cared and everything is fine for me.