I have a question about notation for you: What is meant by the two eighths that are set equal to each other you can see in the picture?

[![Rhapsodie Espagnole, IV. Feria](https://i.stack.imgur.com/ptjSb.jpg)](https://i.stack.imgur.com/ptjSb.jpg)

This from Ravel's Rhapsodie Espagnole, IV. Feria, for piano duet.