"S1" is also standard shorthand for "Semester 1" in academic contexts.
: In some cases, Google Drive may create hundreds of folders starting with "S-1-5-21" during synchronization with Windows 10; these are standard security identifiers and not related to intentional user content. s1 – Google Drive
In media circles, "S1" typically denotes "Season 1" of a television show or series. "S1" is also standard shorthand for "Semester 1"
The most frequent context for this specific Google Drive folder is as a manual distribution point for Anycubic Kobra S1 printer firmware. s1 – Google Drive