If I set up my own filter in knowledge window, this one works by itself quite fine.
Standard ones marked together exclude each other which is fine and standard one + my own one do.
But when I set up such a filter and use it together with another own filter, than it shows what is contained in BOTH filter instead of showing what both include.
Or better said if a and b are in filter one and b and c are in filter two, than marking both shows me a,b,c instead only b.