The appointments view is overridden on the template. Thus the settings will not work here. If you rename this file to anything, then the setting will work. But it will change the design to default SP Medical.
templates/nuron/html/com_spmedical/appointments/default.php
So, keeping the template design, I have used this CSS to Template Options -> Custom Code -> Custom CSS
.spmedical.view-spmedical-appointments #spmedical-specialist-appintment-from .label,
.spmedical.view-spmedical-appointments #spmedical-specialist-appintment-from .custom-checkbox{
display: none;
}