Group Frequency Cap
To determine how many times ads across all the campaigns within a group can be served to a unique device in a set time period, set a frequency cap for the group.
When you've set a group frequency cap, campaign frequency caps still take effect, limiting the number of impressions delivered by each campaign. The group's frequency cap limits the number of impressions shown on a single device by all campaigns in the group.
For example, let's say group G contains two campaigns, A and B, and campaign frequency caps are set to 5 ads every 12 hours. If group G's frequency cap is off, then each campaign could deliver 5 ads in a given 12-hour period.