When dealing with a System-on-Chip (SoC) without built-in nonvolatile memory,  you've most probably had to use an external device to boot the OS (like the Raspbian for Raspberry Pi or a tiny linux distro). Doing so alters visible memory space on the external device used. This article expounds on how to return these devices to their original memory allocation via disk partitioning, with steps extracted from the video below for reference:

Step 1. Run "diskpart.exe"

Start → Run → Type "diskpart" → Enter

Or search for "diskpart.exe" in the search bar.

This opens a command prompt.

Step 2. Check connected disks via the "List Disk" command.

On the opened command prompt, enter "list disk" and check the disk number of your desired external device.

Warning: Do not use the disk number of the memory device running your home operating system (usually assigned to "0" and has a relatively large size > 200G). You may risk losing all your data.

Step 3. Select the disk (external device) via the "select disk <disk number>" command.

For example, to select disk 1, type "select disk 1" and press enter.
To select disk 3, type "select disk 3" and press enter.

Step 4. Delete partition 1 via the "select partition 1" and "delete partition" commands.

Type the command "select partition 1" then press enter.
Type the command "delete partition" then press enter.

Step 5. Clean the partition table and create a primary partition via the "clean" and "create partition primary" commands.

Type the command "clean" then press enter.
Type the command "create partition primary" then press enter.

Step 6. Format the external device.

Simply format the memory device on the "My Computer" window and it will be restored to its original capacity, ready to be turned into another bootable media.

Important Note: Unless you are confident and sure of what you are doing, avoid straying from the instructions especially during memory partitioning. I once tried installing 2 operating systems manually in my computer (Windows and Ubuntu), which required partitioning the hard drive. Unfortunately, I overwrote an important section that boots one of the operating systems and ended up losing the entire partition while troubleshooting. Of course, I had my system backed-up so no data was lost. Hence, being careful when partitioning memory devices is of utmost importance.