"Numbers" is a spreadsheet application available for Mac that competes with Excel. The fact that the .csv file is correctly opened by Numbers shows that there is nothing wrong with the .csv file exported from Practice Optimizer. It maybe an issue with Excel for Mac.
The screenshots below explain how to have the data display correctly. I also listed a second option as well below. Hope this helps!
Select all content on spreadsheet.
Select Data -> Text to Columns.
Select Delimited, then click Next >.
Check the box for Comma, then click Next >.
You will see the the columns sort correctly.
Another way to do this is:
Click File -> Import.
Then click Import.