Adding value in Check Status Message Template fails


I have a numeric value that I would like to add to the status message template of a check, but when I try to add it, the check always shows “Completed(failed)”. According to the documentation I thought that this has to be quite straightforward.

This is what the line looks like (where the field name is “6/4/54”):

Value: ${string(v: r._6/4/54)} 

Hope somebody can give me support.