Hi Linda,
Thanks for reaching out! Setting that option to one month means that the next instance of the event will be created one month prior to that instance. So if you have a weekly event, you should get a new instance of that event (for one month out) generated each week.
Unfortunately there is not a global setting to exclude certain dates from multiple event series at one time. Sorry for the bad news there! You would need to add this exclusion in each series individually.
Please let me know if you have any other questions!
Thanks,
Jennifer