-The number of 1 kB blocks per volume.
-This option overrides the end-of-media detection, and calculation
-of tape size based on length and density. If compression is on this
-limits the size of the compressed output per volume.
+The number of 1 kB blocks per volume. Not normally required, as
+.Nm
+can detect end-of-media. When the specified size is reached,
+.Nm
+waits for you to change the volume. This option overrides
+the calculation of tape size based on length and density.
+If compression is on this limits the size of the compressed
+output per volume.