Nintex Query List filtered by Person

When using Nintex Workflow and trying to use a Query List action and filtering by Person it's tricky to figure out how the workflow is reading the person field.  Here's how I successfully setup the filter:

A person variable is populated earlier in the workflow (I'll call it perPerson)...

1. Create a Text Variable (I'll call it txtPerson)
2. Set Variable action: Set txtPerson = perPerson - User ID Number
3. Query List action: create filter [Person field] is equal to txtPerson