Determing whether or not the file you received by download is the same file on the website from which you acquired it is difficult unless the provider, or someone else, gives you a "hash" value, which is a simple but accurate check. Size alone is insufficient, although a helpful parameter. A "hash" (while more detailed information is available on the web) is, for our purposes and in short, an algorithm which can provide proof that two files are identical. Free "hash" calculators are available - just google. For example, "HashMyFiles" is a small free utility that allows you to calculate the MD5, CRC32 and SHA1 hashes of one or more files in your system. You can then easily copy the MD5/SHA1/CRC32 hashes into the clipboard, or save them into text/html/xml file. There are devotees of each of the different flavors of a "hash", but for this purpose, any one will do. If the known hash matches the hash created for the file you have, the two are identical.
Since ResMed (and many others) do not provide this simple information, the best we can do is infer what that number should be. In my case, I downloaded two separate copies of the file, derived the hash for each, and found it matched. A friend (another hosehead) also downloaded the same ResScan file, and the hash for their file was the same as mine. Therefore, it is reasonable to assume that a good value for ResScan 3.16-SP1 is:
MD5 -- 1116cfec4fcfcd50c8e4e8b7577510f8
SHA1 -- b439a646f6897d972bca9e96e812f79757f992d5
CRC32 -- de9fbd23
If your file has a hash value of one of the above, we know that these files are identical, and most probably are the exact file as on ResMed's site.
Also, if using any of the above, copy and paste is best.
Hope this helps with some troubleshooting.