100% 4k UHD, naturally they just play and can't see the size, I'm going on files to download but maybe they are compressed (MP4) so in reality to stream may be bigger, I don't know.
When I play HD (BluRay) then play a UHD show you can clearly see the difference. I must say that I need to wear my glasses otherwise the UHD image would look no better than HD.
Btw, usually when a UHD show plays it shows it on the top left of the screen, also at the end of the month I still have quarter to half my download quota left.