OGG file starting with OggU instead of OggS in notepad++ [closed]

Recently, I came upon an old file where my OGG file starts with an OggU in Notepad++. When put in Audacity, it plays completely normal, but if I try to change OggS in a file exported with the same version of ffmpeg and Audacity to OggU, it gives me an error trying to play it. How did the OggU get here? Is this possibly a former codec?

I am using notepadd++ due to the fact it lets me view the encoding of the audio and see the ffmpeg version used and the way it was exported