Five images per slide are generated, the used image settings are below, on the advanced tab : Output format JPEG
The first panoramic picture can not be expanded, but the 2nd panorama picture can be expanded (maxImageWidth > imageWidth ).
In the middle of the slide page you see which image has been used on the current device. This is a debug statement which is not displayed in normal albums and also not if srcsets are not used for the current device.
jAlbum image settings