Help Understanding Comparisons In Single Value Charts

I’m a little confused on why I can’t get the comparisons to show the right numbers. I basically have a single value chart that counts the number of records for the previous month that contain a particular related id.

To help illustrate, I basically have a websites collection that you can think of as projects, then I have a conversions collection to track sales. So I’m simply counting the number of conversions that contain the site id of the detail record for the previous. That part works fine.

But when I add in a comparison, I can’t seem to get the numbers to jive.

For example I have 2 filters set in the main single value chart. These include “signup date is previous month” and “related id equals current detail primary id”. Again, this part works fine and is showing the right number of conversions for that particular website for the previous month.

However no matter what filters I add for the comparison, I can’t seem to get the comparison to be for the previous previous month if that makes sense. If we are in march right now, I assume previous month would be Feb. So I just need to know what I need to put in the filters so the comparison will be from Jan.

Obviously I don’t want to have to mess with the filters every month. I simply want to view total conversions for the previous month, and show the comparison that total to the month just before that.

I’m not a programmer, so this is a little confusing to me.