You can order cards on a Kanban by one of two ways: Title or Update Date.

If you would like your cards to be labelled by title, you can name them 1.1, 1.2 etc so that they fall in the correct order. Otherwise it is by the last date they were updated.

To change your preference between Title or Update Date, select the little filter icon in the top right then the "Order By" dropdown box and choose Title or Update Date.