By default, Backblaze attempts to name your computer's backup similar to your computer's name as reported by your operating system, and appends the created date to it (in later versions of Backblaze).
If you wish to change that name to something more descriptive, it's done in the Backblaze software installed on your computer. Just navigate to the Backblaze Preferences, click on Settings, and change the field titled "Online Name for this computer". Spaces cannot be included in the system name.
The change may take a few minutes to be reflected on the Backblaze website.