This looks more of an issue of the testing than the alert message.
What are you putting for your test node/interface/volume?
Remember that it takes the variables from the table of what you specify. So if you have InterfaceID but are alerting from a node, it'll just display ${InterfaceID}.
Also, remember that custom variables are specificed as being either node or interface properties. Not both. Look to see if you can edit it with "edit node" or "edit interface" option.
Lastily, remember that testing ignore conditions and restrictions and goes straight to actions. This means that you can't really test to see if your alert conditions with test alerts, only the information when it sends is correct (so it won't catch that =95.0... makes your alert very unlikely to fire).