using hour and minutes

When you switched from integer to double variables, the compiler also began using double math for you. Your program is intended to separate the hours from the minutes, and back when the values were integers, dividing total minutes by 60 gave you only the hours. But now, the double division gives you a number which includes the minutes expressed as fractions of an hour.

So now, to extract only the hours, you need to employ the math library function Floor which separates the whole portion from the fractions, as shown in this excerpt of your program:

            // Display total minutes excercised to the screen
            hour = Math.Floor(runningTotal / 60);  // <-- note change here
            minutes = runningTotal % 60;

To do it without using Floor, you could subtract the minutes part before you divide, like this:

            // Display total minutes excercised to the screen
            minutes = runningTotal % 60;           // <-- calculate minutes first
            hour = (runningTotal - minutes) / 60;  // <-- subtract them before dividing