Report on End User Inactivity

Dear Zendesk Community,

I would like to create a report that shows end user's inactivity based on the "Time since user login (days)".

First, I have created a Date range calculated metric called "End User Log In Activity (0-30 days) with the Original metric specified as Time since user log in (days) and defined on as Requester sign-in. The date range I selected Last month. 

Next, I wanted to create standard calculated attribute called "Inactive End Users (over 30 days) with the following formula: 

Unfortunately, as you can see I get an error message. Does anyone have any recommendations how to create this report?

Any help is much appreciated!