Time marked as "unbillable" is listed in time manager as Unbilled Time

Hi,

I think that this is a bug: if i'm reporting a time consumption as "unbillable" when i manage time consumption from time admin (to create invoice for example) the time is reported as unbilled even if it was marked as unbillable during insertion. For me, if the time is marked as unbillable this time not need to be listed as "unbilled" because is same to say "to be billed"

Thank you