I believe I know what you're looking for based on your input-output data.
1. Identify the steps = rootNote
2. Determine the interval between the rootNote and the note steps up the scale (number of semitones).
3. find the phase of the rootNote - 60
This algorithm yields precise results:
static int getINMajorScale(int note, int rootNote)
{
    if (note < rootNote) return 0;
    var scale = new[] { 2, 2, 1, 2, 2, 2, 1 };
    var phase = rootNote - 60;
    var steps = note - rootNote;
    var interval = steps == 0 
        ? 0 : Enumerable.Range(0, steps).Sum(step => scale[step % scale.Length]);
    var number = phase + interval;
    return number;
} 
Giving:
static void Main(string[] args)
{
    //rootNote = 60(C), note = 60(C) - output 0
    //rootNote = 60(C), note = 61(C#) - output 2
    //rootNote = 60(C), note = 62(D) - output 4
    //rootNote = 60(C), note = 63(D#) - output 5
    //rootNote = 61(C#), note = 60 (C) - output 0
    //rootNote = 61(C#), note = 61 (C#) - output 1
    //rootNote = 61(C#), note = 62 (D) - output 3
    //rootNote = 61(C#), note = 63 (D#) - output 5
    Console.WriteLine(getINMajorScale(60, 60));  // 0
    Console.WriteLine(getINMajorScale(61, 60));  // 2
    Console.WriteLine(getINMajorScale(62, 60));  // 4
    Console.WriteLine(getINMajorScale(63, 60));  // 5
    Console.WriteLine(getINMajorScale(60, 61));  // 0
    Console.WriteLine(getINMajorScale(61, 61));  // 1
    Console.WriteLine(getINMajorScale(62, 61));  // 3
    Console.WriteLine(getINMajorScale(63, 61));  // 5
    Console.ReadKey();
}