@planedrop
with your setup, you'll have 15 real days of immutability at worst.
here is a little schema with Key backup ( full) and delta . A chain of backup is a key backup and it's delta descendants
mutable backups are noted with a point
K.d.dKdddddKd // in this case the first chain is not protected, because parts of the chain are mutable, but the 2 most recent
K.KdddddKddd // 2 more backups here we have the longest immutables chains
K.dddddKdddd // here is the critical part with the shortest imutable chains : only the last one
K.ddddKdddd //the protetectd chain gros
to ensure a usable immutability of n day, you must have a full backup retention of at least n, and a backup retention of at least 2xn
I am not really sure on the error message that the UI show on backblaze, but the backup will be merged and deleted as soon as possible, when the object lock is lifted.
you can trust backblaze on their object lock, and you cna check the real number of backup stored by looking at the restore tab of XO