/usr/share/acl2-6.3/books/proofstyles/invclock/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/proofstyles/invclock/c2i/
/usr/share/acl2-6.3/books/proofstyles/invclock/c2i/c2i-partial.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/c2i/c2i-total.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/c2i/clock-to-inv.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/compose/
/usr/share/acl2-6.3/books/proofstyles/invclock/compose/compose-c-c-partial.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/compose/compose-c-c-total.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/i2c/
/usr/share/acl2-6.3/books/proofstyles/invclock/i2c/i2c-partial.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/i2c/i2c-total.cert
/usr/share/acl2-6.3/books/proofstyles/invclock/i2c/inv-to-clock.cert