I'm really not sure what the setting was the initial time I exported the image (it was last year). However, currently I was sure to set the resolution to 300. The reason I found this was I noticed that the files I was exporting from LR have been smaller recently. I had played with the export settings so I went back and made sure these were correct (including the res to 300). I then went back to a picture I knew had been a large file and found that it wasn't when it was exported again. Now when I'm exporting new images some are in the high 20's or low 30's as expected and some are in the teens. Same settings.
I appreciate your responses. This is really as much a curiosity for me as I try to understand these programs better.

Yep. The same file from LR.

I have noticed that when I export jpegs from LR6, the files are smaller than in the past. For example, a file that was 28 mb is now 17mb when exported. I realize this is not necessarily a bad thing, but I'm just curious why this is the case. When I look at the settings, the quality is set to 100; "limit file size to" is not checked; "resize to fit" is not checked; and resolution is set to 300. I am probably missing something but not sure what it is. Any thoughts?