The help page (https://developer.apple.com/documentation/applemusicapi/get_catalog_charts) says the results are paginated and can retrieve 50 positions at a time. I'm wondering how many positions total can be retrieved (or equivalently, what is the maximum offset)? Thanks.
There is no official total as it may change over time or under specific circumstances. The presence of the next link in paged responses is an indication there are more results that may be requested. At the time of this response, there are typically up to 200 results available through the Apple Music API.