As per theme design and header structure logo size is best suitable as per our demo site, but you can change logo size if required using custom CSS.
General Option: Navigate to Admin > Appearance > Theme Settings > General From Admin Panel’s Sidebar and then add below mentioned custom css with your desired max-width in CSS Code textarea field and save changes.
.center-logo-header .navbar-brand img, .navbar-brand img { max-width: 156px !important; }
If you want to change footer logo size then you can use below css code with your desired max-width value:
footer img { max-width: 156px !important; }
Retina Logo: Navigate to Admin > Appearance > Theme Settings > Header From Admin Panel’s Sidebar and then add/change value as per your need and save changes.