Scatter Graph X Asis Issue

I was hoping someone could help me with a scatter graph question. On the X Axis the data point is not lining up correctly with the tic mark. I was trying to use dates, i.e., August 1st thru August 31st, and was showing them as the numbers 1-31 in the graph. The data points are lining up one off. The date and assoicated information for the first is aligning with the tic mark for the 2nd. How do I correct this? I have attached a copy of my spreadsheet. Thank you for any help you can give me with this.

Anne H.