I'm not sure what you're asking. It sounds like you're asking how to export all product key, and then it sounds like you're asking how to export product keys within a certain range. Both are possible in LimeLM.
Export all product key: Click the "Export product keys" link of the right hand side of the version page in LimeLM.
Export within a range: Go to advanced search in LimeLM (https://wyday.com/limelm/dashboard/search/ ), select which product keys you want to search for, and then click search. And on the right hand side of the page you'll have an export option.