Measure shows infinity, despite values in base data

Hi there, 

I am currently encountering a strange scenario: 

I have measure A (amount of h´s logged by users) 

Measure B: days logged (distinct count of day posted by logging)

now I want to calclulate the amount of h´s per day . 

si here ´s the measure: 
C = A / B
returns infinity, although cards I use to shw the actual data clearly show values present. 
when I switch the formula of C up to TEST = divide(A,B,0)
it shows a 0. which is also wrong, since A and B clearly have values that can be divided. 
whats the deal here ?