Lightroom CC for Android "How to save to local devicev"?

My photo file size is 400 KB that I import to Lr. I crop and change contrast. Then when I try to "save to local device" I am asked to free up 800 MB on my Android phone. My original file size is only 400 KB. 

I tried with other photos of much smaller file size and no edits, then try "save to local device" and get the same message to free up 800 MB. Why? How can I get around this?