Find an item in the left column that you are interested in choosing and then look in the other columns to matches what you want.
The number next to the radio button indicates the quantity remaining. Click the appropriate radio button to select the item.
You can only select one per column, but you can select one item from as many different columns as you want.
For example: if the first column were jobs in a sports event and the other columns were the different event dates.
You can only select one job for each event date/time, but you could select the same job for each event date/time or different ones for each date/time, your choice.