Need to calculate overall based on the date of introduction

[#1]

Hi Experts,

Please suggest how to calculate the overall where date is lag of first three months based on the date of the product and remaining month values considered for Forecast.

and it is based on the product date. If i select each and every product I'm able to achieve but for the Overall calculation I'm facing some issues.

[sunny_talwar]

Is this something you need on the front end or back end? Can you provide some data, with the expected output to help you better?

[#3]

It is needed on front end in Gauge chart. I will attached some sample data