Begin by having students count forward as far as they can for 15 seconds and then count backwards for 15 seconds from that point. For instance, if a child can count by twos to 42 in 15 seconds, they should start at 42 and count backwards for 15 seconds.
Set timer for 30 seconds total. Master occurs when students are able to count up and back in 30 seconds or less. See example in video above.