How to export design for twitter profile pic size

I am going loopy trying to understand how to export for web in illustrator.

I have created an artboard (size W 157pt H 101pt).

I have tried exporting it 50 different times today. 

When I use export for web and choose variations on the size to both half, 1x and 2x the export, when I go to twitter, the most zoomed out version I can get covers about 60% of the design.  The same result is produced for each of the .5, 1x and 2x versions of the export.

I have also tried exporting for web, specifying a file size of 400 *400 (exactly as specified in the twitter docs). I get the same 60% zoomed out coverage.

How do I create an artboard that I can use as a twitter profile pic? This is so easy in Canva. I can't solve it and I've been trying for half a day in illustrator!

Thank you for the help. I'm feeling pretty stupid right about now.