When you download fit files from your Seestar using the iPad version of the Seestar app on a Mac mini, they files are stored in the “container” that holds the app and makes it think it’s running on an iPad.
To find them, open Finder and select Go to Folder on the Go menu. Enter
~/Library/Containers
In that folder, the app is going to have a random-looking folder name made up of letters and numbers. Open each of those and look for Data/Documents/LocalCache/Download/Scope ID/MyWorks/. That will be your data folder.