De # debian-boot no OFTC:
06:47 <musca> faheem: yes, the dvd series is much bigger, but only the first three images are available as http downloads.
06:50 <musca> for stretch the number of DVD images is 15 http://cdimage.debian.org/cdimage/weekly-builds/amd64/jigdo-dvd/
06:55 <musca> faheem: let me point out: you really don't need those additional images.