Setep 3 and 4 clarifications

[FumingPower3925]

I've tried many times, changing various things, but I cannot seem to get the fstab file correctly modified. All seems right because no red lines appear or anything, but once I try to run the lbu ci, an error pops up that mount cannot find the UUID introduced in fstab.

I find that step a little bit confusing, maybe I've gotten the idea wrong, so a little clarification would be very appreciated, I really want to get this working.