OID hrSystemUptime -1.3.6.1.2.1.25.1.1 correct format

This is somewhat unrelated, but may be helpful in what you are trying to accomplish. I create alerts for when an item goes down and another for when it comes back up.  When it comes back up I include a line to document how long the item was down. You may be able to modify this to help.

Down for: ${SQL:Select '${N=Alerting;M=Downtime}'/1440} Days ${SQL: Select '${N=Alerting;M=Downtime}'%1440/60} Hours ${SQL: Select '${N=Alerting;M=Downtime}'%1440%60;} Minutes 

This is somewhat unrelated, but may be helpful in what you are trying to accomplish. I create alerts for when an item goes down and another for when it comes back up.  When it comes back up I include a line to document how long the item was down. You may be able to modify this to help.

Down for: ${SQL:Select '${N=Alerting;M=Downtime}'/1440} Days ${SQL: Select '${N=Alerting;M=Downtime}'%1440/60} Hours ${SQL: Select '${N=Alerting;M=Downtime}'%1440%60;} Minutes