Hi helifiction,
Thanks for posting a link. I have checked, and I can see the theme limits the width of the header at 1170px. On screens below 1170px, the logo will be on the left edge and the menu on the right. On screens wider, you will start seeing a space either side, as the width is limited to 1170px. As this is related to the header itself (not specifically our plugin), it is something you would need to contact your authors about if you need to adjust it.
Regards,
Tom