Help Required For Fetching True DSO Value in Collection Form

Hi all,

I have got the following formula for calculation of True DSO. But do not have much idea about how we can fetch the value for each component

Formula: True DSO per invoice = Number of days from invoice date to reporting date * (invoice amount/net credit sales for the month in which sale occurred)

Could anyone please help me to know what exactly meant by the below components->

1.Number of days from invoice date to reporting date

2.net credit sales for the month in which sale occurred

It will be very helpful if you have a query/code to determine the values of the above mentioned components.