This happens when cloning from a smaller disk to a larger disk. The space is there, it is just unallocated, and you can't see it from Windows or File Explorer.
You need to go to Disk management. In Windows 10, right-click on the Start button, and you should be able to click directly on Disk management. If not, you can go to Administrative Tools -> Comp Management -> Disk Management.
You will now see your OS and your unallocated space. You can right-click in the used space and click on extend volume to make one large partition that will show the space of the larger drive. Or you can click on shrink volume and make a second partition which is unallocated, convert it to a new simple volume and format it as anything you want. The new partition can be used for a second partition or you can delete the volume giving its space back to the drive and extend the OS drive, likely C, again.
You will only get in trouble if you try to delete the C: drive. And, the easiest thing is just to extend the drive.
The caveat is you can't extend the C: drive directly if there are files between it and the unallocated space. This may be a partition Windows created like a recovery drive. This will be easy one you get to Disk Management.
If you need to you can always download any of the tens of free partitioning software. Acronis is pretty good. Many others.
Samsung. Nice! Make sure you install the software with it. It allows a lot of configuration and tuning stuff. For instance, you may want to trim the drive. I would just go through all the settings and see what is possible.
