test: multi_alarm: Add diagram for timer expiration

Co-authored-by: Tyler Potyondy <[email protected]>

examples/tests/multi_alarm_dont_ignore_previous_overflow/README.md

@@ -1,11 +1,16 @@
 # Test Multiple Alarms (Ensure previous overflowing alarms aren't ignore)
 
 This tests the virtual alarms available to userspace. It sets three
-alarms alarms. The first two overflow and should result in multiple
-alarms under the hood, and a third a 10 second alarm started after the
-second. The first alarm is set first, but expires second (1 second
-after overflow vs 10ms after overflow). The third alarm should expire
-last.
+alarms. The first two overflow and should result in multiple
+alarms under the hood, and a third 10 second alarm started after the
+second alarm fires. The first alarm is set first, but expires second
+(1 second after overflow vs 10ms after overflow). The third alarm
+should expire last.
+
+(Not to scale; demonstrating alarm firing order)
+Alarm 1 (Overflow + 1s) ---Set----------------------Fires--------------
+Alarm 2 (Overflow + 10ms) --------Set------Fires -------------------
+Alarm 3 (Overflow + 10ms + 10s) --------------Set------------Fires
 
 When successful, the first alarm should fire after a clock overflow +
 1 second, while the third should fire after a clock overflow + 10ms +