Math function in tsvb

I am trying to do simple match function on TSVB but it shows no data. If I remove math I can see the value.
What am I doing wrong. I just want to minus some fixed number from it.
totalfreesize is in bytes.

Fixed. just putting out for someone who may be doing same

I had to use L at the end of that large number i.e
params.tf-7000000000L and it works.