[Koha] Reports issues

[Marty Jongepier]

When I do a report on 'issues by category' I get a total of 1466 items. A
note here; I only get results if I don't check the branch - we have only one
branch, main, and if I do check that, I get only zero's. So, if I don't
check that I get a total of 1466 items issued.

We have a total of 6627 items.
When I do a report on 'books not issued' it comes up with a total of 5700.
Maybe I am all wrong, but in my world, 6627 - 5700 = 927, not 1466. (Total
minus items not issued is number of items issued)

So, is my thinking wrong or is there something wrong with the report? And
what can I do about it? Is there any way to test it? 

Thanks,

Marty