Circular Dependencies - Calculated Table

Don't filter the blank values out and then run the below in DAX Studio or Tabular Editor

EVALUATE
ADDCOLUMNS (
    DISTINCT ( 'Query1'[Customer number] ),
    "Customer type", IF ( CALCULATE ( [Total quantity no fob] ) >= 10000, "Top", "No top" ),
    "Total sales", CALCULATE ( [Total sales no fob] ),
    "Total quantity", CALCULATE ( [Total quantity no fob] )
)

By sorting the results on customer number in first ascending and then descending order you should be able to see whether there are any blanks in the result.

You could also try

DEFINE
    VAR T1 =
        ADDCOLUMNS (
            ALLNOBLANKROW ( 'Query1'[Customer number] ),
            "Customer type", IF ( CALCULATE ( [Total quantity no fob] ) >= 10000, "Top", "No top" ),
            "Total sales", CALCULATE ( [Total sales no fob] ),
            "Total quantity", CALCULATE ( [Total quantity no fob] )
        )

EVALUATE
ROW (
    "total rows", COUNTROWS ( T1 ),
    "total customers", COUNTROWS ( SUMMARIZE ( T1, [Customer number] ) )
)

which should give the same number for both total rows and total customers.