bosboot: Boot image is 22995 512 byte blocks.

My mksysb scripts gives the following text on standard error:
bosboot: Boot image is 22995 512 byte blocks.

How come on a Aix 5200-07 aix-system.

I thought this message meant that the tape (/dev/rmt0) is not bootable,
but I read about a limit of 12 MB and 22995 block is less than 12 MB

Or is something else the problem?
By the way, this errors goes on 3 of our machines:

7026-H50
P660
P660

Frank