How do I add a decimal degree reference grid to ArcMap that is multiples of 2?

See attached photos for what I have vs. what I would like. I have tried changing the interval under data frame properties but have had no luck.

[![what I have](https://i.stack.imgur.com/Jxf75.png)](https://i.stack.imgur.com/Jxf75.png)

[![What I want](https://i.stack.imgur.com/TG7I5.png)](https://i.stack.imgur.com/TG7I5.png)