For your workflow, the because of the manner at which the values are generated with the 'Generate' button, you will have to make the max/min have the decimals or it will not include them. The wizard will simply do the direct math. Since your first first value is 5 and specify 10 values the algorithm will then create the values as a straight division. I entered decimals and then the output would have decimals.
From what I understand about your complaint, you want the same types of divisions of classes, but since you are altering the minimum and max value the classes appear to be generalize. Your old class interval was roughly 1.1 and the new one is 1, hence the discrete values. Because of the values you are inputting and the way that the algorithm works, I would call what you are seeing as expected behavior. So to avoid the loss of decimal, then make the interval value of 1.1 (if that is desired). What you are doing is making the data discrete and then specifying a discrete interval without a decimal in the label.