The 15 default User Defined Field Names appear in the following order:
    User1
    User10
    User11
    User12
    User13
    User14
    User15
    User2
    User3
    User4
    User5
    User6
    User7
    User8
    User9
It is suggested you names them like this:

To do this, go in to ACT!
Then go to Edit, Define Fields

Then they would look like this on the screen.
