How are Sigma Rules versioned?

I am using this query to get only the latest Sigma STIX objects

FOR doc IN sigma_rules_vertex_collection
    FILTER doc._is_latest == true
    RETURN [doc]

Currently there are versions

FOR doc IN sigma_rules_vertex_collection
    FILTER doc._stix2arango_note != "automatically imported on collection creation"
    RETURN DISTINCT doc._stix2arango_note

But where do these versions come from?

The data is generated by sigma2stix

sigma2stix allows you to define a Github tag in the original Sigma repo, which is how the Sigma team version rulesets

For each version, sigma2stix generates a STIX bundle, which is then imported to CTI Butler, hence where the doc._stix2arango_note value comes from.