Must be a bug in the build time, as libc6 isn't a dependency until compile time. Compiling the package under natty gives the correct Depends.
Package from repo Depends: libc6 (>> 2.12), libc6 (<< 2.13)
Package built from source in repo with debuild Depends: libc6 (>> 2.13~), libc6 (<< 2.14)
Must be a bug in the build time, as libc6 isn't a dependency until compile time. Compiling the package under natty gives the correct Depends.
Package from repo
Depends: libc6 (>> 2.12), libc6 (<< 2.13)
Package built from source in repo with debuild
Depends: libc6 (>> 2.13~), libc6 (<< 2.14)