The file lowpath is a binary lowpath containing the u64 saveid, however the high word of the saveid is always zero. The mounted file is the savegame image.
=== UserSaveDataForCheck Archive Path Data Format ===
| Upper word saveid
For FS, the file/directory lowpath is a text path in the [[extdata]] filesystem. For FSPXI, the file lowpath is a text path relative to the "/extdata/<ExtdataIDHigh>/<ExtdataIDLow>" directory on SD/NAND, for the extdata image to mount.