My files are larger when I export... HELP

[Nathan25400181guo3]

I have a question regarding AI and jpegs. I am trying to upload my own image to a background photo on Goldcast. It gives me a minimum and maximum size it will take in terms of pixels, I have attached what their website says. I went to adobe, set my art board to what would work, created my piece, and tried uploading but it says its not the right size. I have never had this much trouble and am so confused as to why it wont accept it. Am I missing a step in converting from an AI to a JPEG that is making it bigger than what it should be? I even reduced the quality to make it smaller but it still doesn't work. 

[Test Screen Name]

What is the size in pixels that you want?

and what is the actual size of the file you export? (Checked, not just what you expect?)

if you don't know how to check the actual size, let us know whether you are on Mac or Windows.