Segment and Tag

Hi there, I have a question about tagging and segmenting contacts. Could you please help me with this issue? This morning, I tagged 2610 contacts with "surveillance". In the tag list, I can see the tag I just created with 2610 contacts. After that, I created a segment with only one criterion, "Tagged with surveillance". However, only one contact appears in the segment. Could you please explain what is happening? Is there something wrong with my settings? I would appreciate any suggestions or solutions. Thank you for your help.