issue when getting the nth value with DAX query for sub categories

[Thakshila]

I'm trying to get the nth value using below dataset. I could get the nth value for the correct category. When I added the sub category. It gives the wrong result for the sub categories. It takes the nth value for the sub categories as well. how to avoid this and get the correct result for the sub categories as well. I have attached my .PBI file and pictures of my dax query and results as well.
(https://1drv.ms/u/s!AtRjTEx4ATvZykgX9eSCVl0xBFXa?e=Fz2ctR )
Any help would be appriciated. 
Please check the below screen shot. 

Dax Query

Results    

[wdx223_Daniel · Accepted solution]