scatter chart plotting more than data table contains

You may need to help us understand exactly what is happening and what "errors" are present. Reading between the lines, what you describe sounds perfectly normal for a scatter chart. If I create a scatter chart with x values of 0.625 (15:00), 0.66667 (16:00), and .70833 (17:00) -- then Excel's default axis limits algorithm will choose a value just smaller than the minimum value in the x axis data set for the axis minimum (my version chooses a value of 0.62 [14:52:48]), something larger than the largest value for the axis maximum (my version chose 0.72 [17:16:48]), and a reasonable value for the distance between axis tick marks (my version chose 0.02 [00:28:48] so there would be 4 evenly spaced tick marks between max and min. All of that should be normal, expected behavior for a scatter chart. Sometimes, we dislike the values Excel defaults to for axis max, min, and major unit values -- especially when those values represent time -- but we can easily go into the format axis dialog and enter values that we like better for the axis parameters.

If I'm understanding the "problem" correctly, the solution I see is to simply enter the desired axis parameters into the format axis dialog. If you want the axis to start at 15:00 and end at 17:00 with tick marks spaced every hour, then enter values of 15:00 (0.625 if your version of Excel does not support direct time entry into the fields of the format axis dialog) for axis minimum, 17:00 (0.708333...) for the axis maximum, and 1:00 (0.0416666...) for the major unit.

Did I understand the "problem" correctly, or is there something happening in your spreadsheet that I am not anticipating?