Problem with the radio tuner

When I press the + or - on the tuner, only the number in tens place, hundreds place and thousands place changes I can’t fine tune it to the radio station I want to listen to. For example, I want to listen to 1400 AM and the closest I can get to it is 1396 or 1406. In other words I need to know how to get the number in ones place ( or the number furthest to the right )to change.