If you use the internal RSView built-in acknowledge button, then I don't know of any way to make sure that both RSView stations "see" the acknowledge. Here is what I do:
Create an internal relay bit in your PLC program for "Alarm Acknowledge". Put an Acknowledge button on each RSView screen that is tagged to this PLC bit. Any and every RSView screen can read and wirte to a PLC bit. This is not true of the RSView internal acknowledge, as far as I know. Maybe somebody knows of a way. There probably is one, if a person wanted to spend enough time to track it down. In the meantime, I've got to work on the next project....