Everything you're doing look correct, as well as that SubGit spends some time at that stage. The matter is that SubGit needs to download all the data repository contained at the revision 14300, as well as some other data. For any real-world repository it takes some time, especially if there were any big branches copyings in the history. For old repositories with long history initial replication may take even days, and hours may be considered expected. And that is also normal that the repository size does not change for some time -- most probably, SubGit is still downloading data to a buffer and hasn't yet written any data to the repository. If SubGit does not report any errors in the console and in logs, then everything should work well. This progress bar does not provide much information about the status, indeed, so better to check SubGit logs to make sure it's working. Depending on the initial replication stage, the logs may reside in the same directory where the command was invoked, inside the target repository (subgit/logs subdirectory), or in .subgit directory in current's user home directory.
Okay thanks I will try letting it run for the next week !
For future reference, I actually didn't try the subgit migration and I 'm not able to tell if this worked or not.