Calculated columns as X axis in Bar charts

[Kallenki]

When we create a calculated column that gives the sum with a condition, how can I show that on x axis in bar chart. 

I want to show contracts that are expiring in next 30 days, 60 days and 90 days on a bar chart. I am able to create 3 calculated columns for this but not able to plot. 

The query I used is :

sum(

    if(

        diff_days(now(),${fact_contract.expirationdt_date}) <= 90,

        ${fact_contract.count},

        0

      )

   )

This is my table

I want a plot that should be like:

Any help would be highly appreciated.
Thanks in anticipation