3 3 DURING THE PRECEDING 15 MINUTES
4 4 DURING THE PRECEDING 30 MINUTES
5 5 DURING THE PRECEDING 1 HOUR
6 6 DURING THE PRECEDING 2 HOURS
7 7 DURING THE PRECEDING 3 HOURS
8 8 DURING THE PRECEDING 6 HOURS
9 9 DURING A PERIOD OF MORE THAN 6 HOURS
10 10 UNDETERMINED
15 15 MISSING VALUE
