It's difficult to know based on just the file size. What you need to know is what the pixel dimensions are. If you want a good quality 8 x 10" print then you would probably want to have it printed at 300 PPI. That would require an image that is 2400 x 3000 pixels. You can control the size of the image in the export dialog.
Exporting as a JPG will normally result in a decrease in FILE size, but not a reduction in IMAGE size. So, this is perfectly normal, and I don't see this as unusual or worrisome.
Furthermore, you are looking at the wrong measure. FILE size and megabytes tells you nothing, and will mislead you. Thus, I suggest to you that the comparison of going from 5.7 megabytes to 622 kilobytes is completely meaningless and useless. The IMAGE size, measured in megapixels, (or equivalently dimensions width x height) is what you need to be paying attention to. If you want to print at 8x10, and you use the "usual" level of quality of 300 pixels per inch, then you need 2400x3000 pixels (or more) in your exported photo. But you don't tell us what the IMAGE size is.
Forgive my ignorance, but how do I find the pixel count??
thanks for the help
You can configure your info display so that it shows the pixel dimensions. You can also specify pixel dimensions in the export module. For instance, if you have cropped your image to be 4 x 5./8 x 10 crop ratio then you can specify in your export settings to have the long side exported at 3000 pixels. You can configure your info display options by pressing Ctrl/J (Cmd/J Mac).