/usr/share/acl2-6.3/books/arithmetic-2/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/arithmetic-2/floor-mod/
/usr/share/acl2-6.3/books/arithmetic-2/floor-mod/floor-mod-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/floor-mod/floor-mod.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/
/usr/share/acl2-6.3/books/arithmetic-2/meta/cancel-terms-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/cancel-terms-meta.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/collect-terms-meta.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/common-meta.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/expt-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/expt.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/integerp-meta.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/integerp.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/mini-theories.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/non-linear.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/numerator-and-denominator.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/post.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/pre.cert
/usr/share/acl2-6.3/books/arithmetic-2/meta/top.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/
/usr/share/acl2-6.3/books/arithmetic-2/pass1/basic-arithmetic-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/basic-arithmetic.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/expt-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/expt.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/inequalities.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/mini-theories.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/numerator-and-denominator-helper.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/numerator-and-denominator.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/prefer-times.cert
/usr/share/acl2-6.3/books/arithmetic-2/pass1/top.cert