On the Roland TD-17, each backup to an SD card is saved under one of up to 99 "Bank" numbers. Banks let a single SD card hold multiple backups instead of requiring a separate card for each one.
Each backup stores all settings in the TD-17 at the time of backup, including all 100 kits.
Saving a new backup to a Bank that already contains data overwrites and erases the previous backup in that Bank. To keep an existing backup, choose an unused Bank number for the new one.