To top that, as far as I understand, 7 is also OTT:All displays must support 4, 5, and 7 through HDMI. 4 and 5 are 0TT. While 7 is reserved for UHD BluRay.
"The dual-stream solution includes two video streams, known as the Base Layer and the Enhancement Layer.
The Base Layer shall conform to the requirements of one of the following Interoperability Points: the DASH-IF IOP Main Interoperability Point, the DASH-IF IOP UHD 4k Interoperability point [i.e. Dolby Vision Profile 4 base layer] or the DASH-IF IOP UHD HDR10 Interoperability point [i.e. Dolby Vision Profile 7 base layer]."
Standards ecosystem of Dolby Vision: