How do I resolve an incorrect backup path

I've followed the direction at I'm trying to migrate a single site into my multisite and I'm having an issue with getting the correct path. When I go to import the backup from the single site and type the new blog location into the lookup field it returns an incorrect URL (with some redundancy) to upload the restore to. The incorect URL generated is

where it should be

I've not found a way to edit the URL so consequently everything except the homepage returns 404s after restore. I'm using the sub-domain address for the move/restore as I've not changes the DNS for the single site yet.
can you advise what I'm missing here to get it to restore to the correct path?