Count occurrence with condition

Hello dgdgdg122db 

We need just a few measures to get what you are looking for.

A count of all the rows, this we will use for filtering later.

Line Count = COUNTROWS ( 'Table' )

A count of the distinct customers (the 20)

Buying Customers = DISTINCTCOUNT ( 'Table'[Client no] )

The first time buyers

First Time Buyers = 
CALCULATE ( 
    [Buying Customers], FILTER ( VALUES ( 'Table'[Client no] ) , [Line Count] = 1 )
)

And the returning customers

Returning Customers = 
CALCULATE ( 
    [Buying Customers], FILTER ( VALUES ( 'Table'[Client no] ) , [Line Count] > 1 )
)

I'm not sure what you mean about the filter on position 10 but the position filed can be added as a page level filter and that will limit all the measures above to only calculate against the lines in position 10 if that is what you are looking for.

I have attached my sample file for you to look at.