Each column in the data table represents a variable in your experiment. To name the column point the mouse cursor over the letter at the top of the column and double click the mouse button. Each column is represented by an upper case letter in the alphabet until you rename it. When you double click on the column name make sure that your data type does not say text. If it does then the program will think that the column you are using is text and not numbers.
Float is a generally excepted data type.
As opposed to integers, this means that you can have decimals. You can also change the format if you wish to scientific notation, etc. This is a default for the program. This feature is similar to Microsoft Excel. If you are more familiar with Excel then you can create a table in Excel and simply cut and paste the columns into Kaleidagraph.