That plugin is using a class of wrapper (really bad idea, that, since almost every web site has a “wrapper”) with this code:
min-width: 1100px;
I’m sorry to say it, but that is really crap coding. The plugin author should know better.
Try adding this to Graphene’s custom CSS feature:
#Login_Form_id .wrapper {
min-width: 100px;
}
This isn’t really a Graphene issue, but I hope this works for you. If it does, please take it up with the plugin author, and reference this thread.