80 MB means 80 megaBYTES. So if it's just an image, you have nothing to worry about as the size will not be that big. If you are uploading a video on the other hand, then it would come into play.

1kb = 1024 bytes (a lot of people usually just round to 1000)
and 1 MB = 1024 kb
so 80 MB would be 81,920 kilobytes, or 83,886,080 bytes.

                                                                                                                    

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