WMV (Windows Media Video) is a video codec developed by Microsoft. It's commonly used for online video content. A WMV file with a size of 3358g ( possibly gigabytes) would imply a high-quality video or a lengthy recording.
provides specific details about the nature of this particular archival set: WMV (Windows Media Video):
The "3358g" suffix is a common shorthand in archival communities to denote the file size (3358 MB/Giga-scale) to help users verify they have the full, uncorrupted set.