Press "-" in pulse mode to change between current and maximum/average pulse. Pess "M" and hold for 2 secs to set the pulse limit values. Upper limit use "-" and "+" to select and then confirm with "M". Do same to set lower limit.
Update on the sheer quality of this accessory:
About a month ago it went through a full washing machine cycle at 30 degrees (including 600 rpm spin). On removing it from what I thought would be its watery grave, I noticed water under the glass and a blank display etc. Whipped the battery out and placed it in intensive care (airing cupboard) for 4 days. Battery back in on day 5 and it powered up without a problem. Reset it and it's worked perfectly ever since - really impressed!