Improve time alarm doc

Fixes #7406

Author: tannewt

shared-bindings/alarm/time/TimeAlarm.c

@@ -51,11 +51,12 @@ mp_obj_t MP_WEAK rtc_get_time_source_time(void) {
 //|         ``monotonic_time``, or when `time.time()` would equal ``epoch_time``.
 //|         Only one of the two arguments can be given.
 //|         The alarm is not active until it is passed to an
-//|         `alarm`-enabling function, such as `alarm.light_sleep_until_alarms()` or
+//|         `alarm`-enabling sleep function, such as `alarm.light_sleep_until_alarms()` or
 //|         `alarm.exit_and_deep_sleep_until_alarms()`.
 //|
-//|         If the given time is in the past when sleep occurs, the alarm will be triggered
-//|         immediately.
+//|         If the given time is already in the past, then an exception is raised.
+//|         If the sleep happens after the given time, then it will wake immediately
+//|         due to this time alarm.
 //|         """
 //|         ...
 STATIC mp_obj_t alarm_time_timealarm_make_new(const mp_obj_type_t *type,