returning customer count

This is really confusing. 

I've made my own example dataset:

The calculated column "Column" is simply:

Column = 
VAR ID_ = [did_groups]
VAR DATE_ = [ltime]

return

IF(CALCULATE( SUM([lon]);
ALL(Table1);
Table1[did_groups] = ID_;
table1[ltime] < DATE_
)
>0
;1;0)

Which gives me 7.

Then i use the measure:

Measure = Calculate(distinctcount([did_groups]);Table1[Column]=1)

Which removes 1 and give's me 6. Which should be the correct number of returning customers in the dataset that I made.

:->