For example if the Daparture Date is Oct 11th and the Return Date is October 13th the repeating section would have 3 rows for each day away/returning. I have a hidden calculated field that does this calculation but don't know how to use this 'Days' calulated field to set the number of rows to display. I have attached the form.
repeating section's default/min/max rows are not configurable at runtime.
you can see how it could be done eg on this link https://community.nintex.com/message/64329-re-want-to-add-a-new-row-to-a-nintex-forms-repeating-sect...
BUT, if user changes dates and days difference lowers, you would likely need something similar to delete rows.
I affraid of this might get too complex...
I'd recommend little different approach.
instead of pre-creating rows within repating section, let the user add/delete/manage rows as needed.
to make sure he/she creates as many rows as calculated days difference, setup a validation rule that prevents to submit form if the two differs.
something very similar I've depicted on following link, just there it was for formatting rules.