From a quick glance, it looks like `leftoverdebs` is initially a list of packages, but in the suite/compoenent loop, leftoverdebs is assigned to the package sizes.
...
leftoverdebs=$(printf "$leftoverdebs"|tr ' ' '\n'|sort -u|tr '\n' ' ')
....
leftoverdebs="$(get_package_sizes "$m1" "$pkgdest" $leftoverdebs)"
....
error 1 LEFTOVERDEBS "Couldn't find these debs: %s" "$leftoverdebs"
The output number appears to be the package sizes. Very confusing output error message indeed!