Campaign picking up different candidates for same Audiences criteria used in different campaigns

Summary:

Hi All,

We have two campaigns with same criteria for Audiences(External Candidates).There are around 20000 plus candidates.It is limiting sending email to 10,000 .But , problem is it picking random candidates.Lets say around 2000 emails/candidates are it is picking different in these two Campaigns.Is there any logic or criteria for campaigns pullin gthe specific canidates.We don't see any specific pattern or criteria.

Thank you

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