Certificate "IssuedBy" "Daystoexpire" to be displayed...

Yes, if you want to capture text attributes about each instance, that will be in the discovery script. if $_.Issuer contains the text, you should be good. 

Is your DS script or batchscript? That will drive what the output of your script needs to look like. Assuming script:

I'm not a PowerShell guy, so forgive me. Does your collection script actually output something like this?

daystoexpire: 3

Since the "IssuedBy" will be an instance level property and not a numeric datapoint, the above should be what your output looks like for script.

For batch script, it would need to look like: 

215B79E278B3396EDC4973089E8Z1EDE762FEF04.daystoexpire: 3