Convert "Down Time" which is in minutes, into hours:mins

How do I convert the output of "Down Time" which is in minutes, into hours:mins:secs?

For example, using the variable ${N=Alerting;M=DownTime} we get the "Down time" in minutes.  one of our nodes was down for 213 minutes..

How can I convert this calculation so that when we get the "Node Reset email" we'll see the "down time" in hours:mins?

Thanks!