When it’s Internal Storage.
The android system only allows one file path to access either internal or external storage. If your device has both internal AND external storage then the external storage is usually accessed as a subfolder of the internal storage.
e.g. The Droid Razr has both internal and external storage.
The internal storage is accessed on the path /sdcard whilst the external storage (the real SD Card) is accessed via /sdcard-ext
The paths above are an example only and totally depend on the device and how the manufacturer set up the storage. There is no way a developer can tell if storage is external or internal.
What this means is that if you backup from Password Safe using the SD Card option, you could actually be inadvertently saving to your internal storage.
Check the actual path of your external storage using a file manager program. e.g Explorer otherwise you may have a nasty surprise if your device dies and the only backups you have are locked inside your broken phone.
The default save location is “/sdcard/Kuffs Backup Data”
Check your file path