mt command questions

[Sean Murphy]

I am learning about backing up to tape and have made quite a bit of 
progress with the mt command.  I understand what the fsf option does.  
There are other options however and would like to understand them as 
well.  I am looking at the man page and have tried googleing them with 
not a lot of luck.  the fsr and fss options I understand they would fast 
forward but what is "count records" and "count setmarks" considered and 
how would I use them?

Thanks