What is the new Twitter Header Dimensions and how do I change?

Recommended Twitter Header Dimensions
Twitter’s recommended dimensions for header photo is 1252px in width x 626px in height OR 1500px in width × 500px in height but it didn’t work well when I uploaded the header.

My twitter header dimension is : 1252 x 388

How To Change Your Twitter Header

Go to Edit Profile.
Click the “Change Header” button, then click “Upload photo”.
Hit “Save Changes” button.

End results of new Twitter Header