Subtotal of duplicate rows (one subtotal per duplicate, keeping all duplicate rows)

I've got a column with 1's for the duplicates and 0's for unique rows, but want to have a duplicate subtotal... can't for the life of me figure out a way to only display the subtotal once (I've calculated the total by grouping and summing, but the total displays on each duplicate row, not once for each. If I could find a way to get the first duplicate to have a 0 and the rest to have a 1, I could then do a calculated if/then column, but I don't have any ideas... Thoughts?
Thank you in advance!

Is this question related to Power Query?

Perhaps post a sample sheet showing data and desired results

Sorry, it is a Power Query question. I'm new to posting on forums, so I need to figure out how to post better examples. Been super busy last couple of days and haven't had a minute. I'll try posting an example later today. Thank you.

Example File

Please see the attached for the current and desired states of the data.
Thank you for your help!

Try this below.
Regards

Wow this is fantastic, thank you. How/where have you learned so much in power query? (any tips on where to go to develop my skills, other than of course, Ken Puls's book, and forums?) Also, when you grouped the rows and made the table column, you were using the editor and not the UI, correct?