Hi Nintex,
There is an error in the NAC Online Help Manual for the Functions - first and last.
URL: https://help.nintex.com/en-US/nwc/Content/Designer/Functions/first.htm
When used without the square brackets, the following error is displayed.
The description in the function is more accurate. the string must be enclosed in square brackets.
URL: https://help.nintex.com/en-US/nwc/Content/Designer/Functions/last.htm
The description in the function is more accurate. the string must be enclosed in square brackets.