What is the field meta key option
Every field has a "unique meta key" setting that must be filled. This is automatically created for you when you create the field. The meta key determines how the field will be stored into the database of your website. If you do not need to do any custom development you probably do not need to customize this field.
This means that the full metakey name is wpum_field_11. If you change that to anything else like "job_title", the metakey will be wpum_job_title.
Here you can find an example of the get_user_meta function retrieving a WPUM field value.
get_user_meta( $user_id, 'wpum_field_11', true );