"Data type mismatch in criteria expression"

Hi! I'm currently developing a queuing system, when I executed my program a message box appeared that said "Data Type Mismatch in criteria expression". I don't have any idea what that expression means. the code below is the last line of codes I modified before the message appeared. Can anyone help me out? Thanks!

What I have tried:

If (Queue.Label1.Text <= FrmNumApp.NumCon.Text) Then
            My.Computer.Audio.Play(My.Resources.DoorBell, AudioPlayMode.Background)
            Queue.Timer4.Enabled = True
            Dim speaker2 As New SpeechSynthesizer()
            Dim speak2 As New Prosody()
            
            speak2.Duration = 5
            speaker2.Rate = -5
            speaker2.Volume = 100
            speaker2.Speak("Now serving number " + Queue.Label1.Text)
            speaker2.SelectVoiceByHints(VoiceGender.Male)

        ElseIf (Queue.Label1.Text > FrmNumApp.NumCon.Text) Then
            MessageBox.Show("You are calling an invalid number!")
        End If

Tags: Visual Basic