If I use a variable in the Instance Name, is there a way to use only the first N characters?

Example:

Authorization for Records Destruction: {/dataset/RecordsDescription}

If a user inputs a long Records Description, I would only want to use the first 20 characters. Is that possible?  I'm thinking I could create a hidden field on the form, manipulate the RecordsDescription value somehow, and use the variable for that field, but perhaps there is a way to use "in-line" functions with variables that I don't know about.  Something like Left(20,{/dataset/RecordsDescription}).

We are using on prem 10.4.5.  Thank you.