Is WP tiles meta looking for custom field names/values ? What is it looking for?

Hello,

is wp tiles looking for custom field names/values or meta box names/values?

I am using a form WP plugin called “USP pro”. Submitted posts have added custom fields, which should be displayed with the byline feature of wp-tiles eg.: %meta:usp-author% but the info is not displayed. Therefore I am curious, if WP-tiles is looking for custom field names/values or meta box names/values?.

Thanks