Let's take an example:
us1: GRANT SELECT ON table to us2 WITH GRANT OPTION;
us2: GRANT SELECT ON table to us3 WITH GRANT OPTION;
us3: GRANT SELECT ON table to us2;
All permission grants are positive edits, so it does not revoke any grants at all. If it would not work like that, granting rights would become nearly impossible:
GRANT SELECT ON db.* TO user1
GRANT ALL ON db.abc TO user1
Would then only result in the last grant, making it impossible for you to build elaborate grants.