Hey idanlazar, As @curtiso mentioned that The 1 day total population
indicates the total number of IDs qualified into the audience as of the
past 24 hours. you can also check the rule of your Trait whether the
rule is capturing any specific audience or all audiences of your
website. You can also check the Trend Report which will help you in
understanding the trend of your Trait's data. Thanks Prabhat Upadhyay