The only thing I read about on the official Synology website is that this will happen when you reset the NAS, but you won't lose any data (although not guaranteed). Only the configuration and settings will be lost, but that shouldn't be a big issue. If you don't want to lose your data making a backup is highly recommended of course.
Thanks R0KH, true. The update happened with no data loss but I had to re install packages and re configure all which wasnt a big deal.