Complex sentence: Defending the person who has the disc, or marking, is allowed and then that person may count to 10 (seconds) and if it has not been thrown when the defending player reaches 10 the disk is given to the other team.
Split into simpler sentences: Defending the person who has the disc, or marking, is allowed. That person may count to 10 (seconds) and if it has not been thrown when the defending player reaches 10 the disk is given to the other team.