To suppress the output for the 0 records, you could use a SKIPIF field, coded along the lines of:
{SKIPIF{MERGEFIELD LetterType}= "0"}

I have no idea what you'd done with the IF field in in your image. If you want me to investigate it, you'll need to attach the actual file to a post.

PS: Please post your images etc. here, not on a 3rd-party website from which they might disappear.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]