Code:
/KNOPPIX/etc/apt/apt.conf.d/00knoppix
has the correct mention:
Code:
 // Debian/stretch is the "stable" release in this version of KNOPPIX!

The following two binaries contain the string:
(1) srcpkgcache.bin
Code:
/var/lib/apt/lists/ftp.de.debian.org_debian_dists_stable_Release....ftp.de.debian.org.....stable....9.4.....Debian....stretch..
(2) pkgcache.bin
Code:
/var/lib/apt/lists/ftp.de.debian.org_debian_dists_stable_Release....ftp.de.debian.org.....stable....9.4.....Debian....stretch...
So it figures why 9.4 is the base stretch. Now to upgrade to 9.11.0, the final Stretch.

Need to find if similar binaries have the above string:
Code:
ftp.de.debian.org.....stable....9.4.....Debian....stretch
The directory /var/lib/apt/lists is found to have the following:
auxfiles
debian-knoppix.alioth.debian.org_._InRelease
debian-knoppix.alioth.debian.org_._Packages
ftp.de.debian.org_debian_dists_experimental_contri b_binary-i386_Packages
ftp.de.debian.org_debian_dists_experimental_InRele ase
ftp.de.debian.org_debian_dists_experimental_main_b inary-i386_Packages
ftp.de.debian.org_debian_dists_experimental_non-free_binary-i386_Packages
ftp.de.debian.org_debian_dists_stable_contrib_bina ry-i386_Packages
ftp.de.debian.org_debian_dists_stable_main_binary-i386_Packages
ftp.de.debian.org_debian_dists_stable_non-free_binary-i386_Packages
ftp.de.debian.org_debian_dists_stable_Release
ftp.de.debian.org_debian_dists_stable-updates_InRelease
ftp.de.debian.org_debian_dists_stable-updates_main_binary-i386_Packages
ftp.de.debian.org_debian_dists_testing_contrib_bin ary-i386_Packages
ftp.de.debian.org_debian_dists_testing_InRelease
ftp.de.debian.org_debian_dists_testing_main_binary-i386_Packages
ftp.de.debian.org_debian_dists_testing_non-free_binary-i386_Packages
ftp.de.debian.org_debian_dists_unstable_contrib_bi nary-i386_Packages
ftp.de.debian.org_debian_dists_unstable_InRelease
ftp.de.debian.org_debian_dists_unstable_main_binar y-i386_Packages
ftp.de.debian.org_debian_dists_unstable_non-free_binary-i386_Packages
lock
partial
security.debian.org_dists_stable_updates_contrib_b inary-i386_Packages
security.debian.org_dists_stable_updates_InRelease
security.debian.org_dists_stable_updates_main_bina ry-i386_Packages
security.debian.org_dists_stable_updates_non-free_binary-i386_Packages
security.debian.org_dists_testing_updates_InReleas e
*_Sources