The secondary logo dimensions can be adjusted by its background-size CSS value. This article describes how a secondary logo can be displayed through the site editor. The background-size CSS value can be set on the same left sidebar once the secondary logo is enabled, as shown below.
Different options can be used to fit the logo to your preferred design, such as auto, contain and cover. Numerical values can also be used with their unit of expressions, such as percentage or pixel.
More information can be found upon hovering over the tooltip (question mark icon next to the background-size field) or in this resource site.
To set values for the secondary logo background-size property:
1. Display the secondary logo through the site editor. You can refer to this site for more details.
2. Indicate your preferred setting for the background-size. The background-size will allow you to specify the size of the secondary logo. You can set the logo size using percentages (e.g. 50%, 80%, etc.) or one of the three options in the dropdown:
auto - the image is displayed in its original size
cover - scales the image so that the content area is completely covered. Both its width and height are equal to, or may exceed the content area.
contain - scales the image to be as large as possible, but both its width and its height must fit inside the content area. (recommended option)
3. Click on Done Editing.