Okay, just imagine Kate went to an Other World, she's back and miss to close the gate.
During the Mythos Phase, the Myth Card indicates a gate to open at Kate place.
What happened exactly ? I have an idea, but wanted to be sure. I would say that there is a monster surge from that gate and all the monsters which should have appeared on Kate place are prevented. So 3 gates (A,B,C) and 4 monsters. Usually A will have 2 monsters and B & C one each. But there, with Kate on gate A, there are only 2 monsters appearing on B & C.
Right ?