in the template, the code that writes the label is:
<?php echo(str_replace("_"," ",$pkey)); ?>:
The form element name that is passed in is:
Registration_group_First_Name
the above code is removing the underscores, you can edit that to also remove the Registration_group_ portion or the name:
<?php echo(str_replace("_"," ",str_replace("Registration_group_","",$pkey))); ?>: