Here is what I put to config.
I have no idea what that filemark is. So if its wrong, I am not lying ;)

define tapetype SURESTORE-1200E {
    comment "HP AutoLoader"
    length 12000 mbytes
    filemark 100 kbytes
    speed 500 kbytes
}

>>>I believe the paramaters you give are not the real parameters
>>>of the config that is running, or I must be very stupid.
>> 
>> 
>> Ok, you got me. I never said it's 3.9G. Actually the tape holds 12.0G.
>> Sorry Guys, I'm not joking, just trying hard.
>> The config below was just the example and I did not change it :-(
>
>Did not change in the mail? Or did not change it the Config?
>It's better that you don't lie to Amanda.  It works much better if
>she has more correct info.
>
>
>
>-- 
>Paul Bijnens, Xplanation                            Tel  +32 16 397.511
>Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
>http://www.xplanation.com/          email:  Paul.Bijnens AT xplanation DOT com
>***********************************************************************
>* I think I've got the hang of it now:  exit, ^D, ^C, ^\, ^Z, ^Q, F6, *
>* quit,  ZZ, :q, :q!,  M-Z, ^X^C,  logoff, logout, close, bye,  /bye, *
>* stop, end, F3, ~., ^]c, +++ ATH, disconnect, halt,  abort,  hangup, *
>* PF4, F20, ^X^X, :D::D, KJOB, F14-f-e, F8-e,  kill -1 $$,  shutdown, *
>* kill -9 1,  Alt-F4,  Ctrl-Alt-Del,  AltGr-NumLock,  Stop-A,  ...    *
>* ...  "Are you sure?"  ...   YES   ...   Phew ...   I'm out          *
>***********************************************************************
>
>