Please give more details. What version of Lightroom? What OS? How did you check the file size in and outside Lightroom? Lightroom is a database. It does not contain the physical images, only a link to them. That means that your claim is probably based on a misconception.
Hi, I’m very new to this whole thing so bare with me. I’m am on on a plan with adobe for lightroom. When I upload it it comes in with a very long number which show as the bottom of the screen that I don’t recognise. Then when I export them to a folder on my desktop the file is in KB instead of MB.