If you create a working hour profile the moment you take a look at the users calendar you´ll see a light blue indicator at those hours the user is available. But you can also create breaks and time-offs as you know. The moment you´re doing this you´ll notice that the blue indicators are not correct if your time-off won´t be touching the last business hour of your working hours.

Please correct this and make sure that the blue indicator is showing the correct available time-frame