Updates go to </Library/Updates>; that includes some receipts.
Receipts (not all) for installed updates go to </Library/Receipts>. They will have the same icon and .pkg file name extension as updates, but they're different.
You shouldn't touch items in </Library/Receipts>.
You may delete items in </Library/Updates>. However, you show those items as totalling 300MB. That's not even peanuts, that's sunflower seeds. You will gain nothing, and you're wasting your time on such trivialities; moreover, as a rule of thumb, you shouldn't delete anything from </Library> unless you know exactly what it does and why you won't ever need it.
Get an app like GrandPerspective, or WhatSize, or OmniDiskSweeper. Then you'll be able to figure out what is worth your time deleting to free space on your hard disk.