The firstname.lastname@example.org is a dummy account which allows from (1.6.6) version of the plugin to gather all the cookies that are on the website using ’Detect cookies’ option.
The purpose of the dummy account is to activate the cookies which normally would only show when some action is made on the pages (for example added product to cart.)
This account should be removed after the scan of the site is done. If you don’t want it to be constantly created, on path Ultimate GDPR > Cookie Consent - Preferences change the ”Choose how often cookie check should be performed” to Never. It will stop the plugin from creating this account constantly.