Not Needed Usermeta to remove

i found ‘_um_last_login’ and ‘form_id’ usermeta in the db.. but wondering what are the use of those 2 meta value? as far as i know ‘form_id’ refers to Default Registration form id and it is creating same value for each user.. so how can i remove them or prevent them from generating? i don’t see any usage of ‘_um_last_login’ in my site? so i want to remove it… Please help