Before the feature of snooze was introduced in clocks, they had a standardized configuration. The snooze button was introduced, its apparatus had to be collaborated with existing configurations of clocks. The clock engineers had two options for snooze configurations. Either to configure it in a way such that it goes off after 10 minutes or it goes off before 10 minutes.
A study revealed that if a person slept for 10 minutes, they fell into deep sleep. So the engineers set the snooze buttons go off after 9 minutes.
However in today’s date this feature in clocks is not relevant. The users can determine the snooze time of their clocks themselves.