The two parameters to Range are the first number and the count of elements to produce (not the last number).

// prints 1,2,3,4,5,6,7,8,9,10
Console.WriteLine(string.Join(",", Enumerable.Range(1, 10)));

// prints 10,11,12,13,14
Console.WriteLine(string.Join(",", Enumerable.Range(10, 5)));