This article describes why the upgrade image name and the backup partition image are different.
root@jtac-srx1500-r2064> show system software backup
Backup JUNOS package information:
File name: /recovery/images/install-media-srx-700e-junos-23.2R1-S1.6.tgz
File size: 1174624616
This is the recovery image, which is present in the device.
When you perform the rollback, the device will be rolled back to the version mentioned in the backup.
The recovery image will be that image from which the device was upgraded previously.
For example:
You have the image install-media-srx-700e-junos21.2R3.8.tgz, so the device was upgraded from 21.2R3.8 version to current version 22.4R3-S2