VBA Loop Script For List Of Numbers

I'm trying to write a vba loop script for a list of numbers. The scrip should do:

1.Check if the numbers identical.
2.If the numbers identical give a serial number that will count the identical numbers.
3.if The numbers do not match, then start a new series of serial numbers counting.

I have the script for the serial number. Script so it will have the conditional part - so the serial number counting will start over when the number in the list changes.

Sub counter()
For i = 1 To Cells(Rows.Count, "B").End(xlUp).Row
If Cells(i, "B").Value "" Then
Cells(i, "A").Value = i - 0
End If
Next i
End Sub

The final result should look like this (the colores are not needed)