Powershell can't find AD-user with simple single commandline

Question

I have multiple users called Anna, but when I use the following powershell command line only 2 out of three shows up in the ps-prompt.
Get-ADUser -filter {givenName -eq "anna"} I also tried
Get-ADUser -filter {givenName -like "anna"} still only gives me two out of three users called Anna.
I  don't get any errors, and it gives user info from the other two called Anna. I have checked that the last one also exists and isn't disablet.
What is wrong here?
I run PowerShell from my own Win 7 32bit Workstation in an elevated prompt I have enabled ps-remoting and Winrm and also ran the Wsman command so I can remote enable to a server og pc via powershell. I have also created a local ps profile
that always import the Activedirectory module.

Answer 1

You're right, she was created with her firstname and middlename in AD where you type in the firstname.
But when I used your suggestion and added a * after her firstname she popped up. :)
This is what I wrote: 
Get-ADUser -filter {samaccountname -like "anna *"} | FL SamAccountName, SurName, GivenName
The * after her firstname gave me the results I wanted. Thanks for the help.
Simon