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Please help me to use the right word order in the following sentence. I highlighted the needed places in dark-blue:

"Attention! Total size of the files, which are uploaded at one time, should not exceed 125 Mb. For instance, you may upload five mp3 files at one time, each being 25 Mb. Or, say, you need to upload 60 photos, 2 MB each. Just remember that you need to stay within 125 Mb. "

Which variant is correct? Or none of them is correct? If none, please advice. Thanks.
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I'd write:

Attention! Total size of the files that are uploaded at one time should not exceed 125 Mb. For instance, you may upload five 25-Mb mp3 files at one time, or sixty 2-Mb photos. Just remember that you need to stay within 125 Mb.
Comments  
Many thanks! Just in time [A]