Sorry for not making your clear.As told on previous reply, logo dimension will remains constant on both page width 1140px. So you have to take the image accordingly.
When you set page width of 1400px then your page width will be in-between 1200px to 1400px depending upone your screen resolution. We had attached screenshot of the image measuring on larger( 1600×900 ) and smaller desktop( 1366×768 ). Please have a look on the attached screenshot.
Hope this clarify your issue.