Action Classifier Annotations Error in Create ML

According to the Building an Action Classifier Data Source Article in the Create ML Documentation ,the start and end times can be a "A string of hours, minutes, and seconds, for example: 05:01:03", however when I load the training data into Create ML I get the following error " Unexpected value is not Double or Int in 'end' csv column". What I have in the CSV file is this

video1.mp4,test_label,0:01:00,0:01:01

Is there a trick to getting this to work or can it only be a int or a double?