Filter through different dimension with conditions


I’m pretty new to eazyBI and want to be able to filter out issues based on two different dimensions.
We classify our bugs with two custom fields in Jira (Probability & Severity). Then we have a matrix that provides us with how critical the bug is. For example if a bug has 4 in severity and a probability above 3 it is 75/100 critical.

I need to be able to create a filter to see the trends of different criticality of bugs. Therefore I want to create a calculated member based on these two dimensions to filter out specific bugs.

My take was a function like this:

[Severity].[Severity] = 4
([Probability].[probability] >= 3

It doesn’t work. How should I do this?