Setting up watchdog_set_period to max value causes reboot

Setting up watchdog_set_period to max value causes reboot

I don't much about how watchdog timer works in embedded environment and I
am facing issue related to watchdog timer
Maximum time out value defined in one of the macro is 55 and when we try
to set up this value from watchdog_set_period function ,our board is
getting reboot
#define Max_time_out 55
watchdog_set_period(int period)
where period = 55
Now is it something expected or how what is the reason for reboot
We are writing this period value to some driver which we are accessing
through file descriptor.