Distinctcount with FILTER true/false

HI guys, 

I'm trying to get number of clients who meet certain conditions. 

Clients who didn't have any sales before certain period and who have sales after certain period. 

So I have 2 measures:
before = CALCULATE([Total Revenue];DATESBETWEEN(Calendar[Date];DATE(2018;03;01);DATE(2018;08;31)))+0
after = CALCULATE([Total Revenue];DATESBETWEEN(Kalendarz[Date];DATE(2018;9;1);date(2018;12;31)))+0

Then I've used IF funciton:
True/False = IF([before]=0 && [after]>0 ;"true";"false")

Now I'd like to count the "true" clients so I tried something like this:

 True count = CALCULATE(DISTINCTCOUNT('Clients'[Code]);FILTER('Clients';[True/False]="true"))+0

and it works in most cases, but not always. As you can see on the screenshot below: B193A is marked as "false" but it is counted as "True".
I'm missing something here but not sure what it is;)