Pan Initial Positioning Issue with Panagraphic Images Less than 360 degrees

Firstly, in the properties panel, select the option panfov as partial "210" or the actual pan degrees of your panoramic images.
Secondly, set the pan values as initial:-180, min: -180, and max: 30. Because the images you import are not 360 degrees, the minimum value will start from negative 180 degree. And the minimum value plus the maximum value equals the whole pan degrees of the panoramic image you have imported. At last, you'll get a panorama starting to play from the left side of the image to the very right side.