Follow these instructions to verify a download
Downloads that your browser say are finished are not necessarily complete or intact, this happens less these days but it is still possible that a download has been corrupted. Verify your download using the displayed checksum for safety/sanity.
Your windows should have the utility 'shasum' installed, open terminal in your download directory or where ever you have the file stored and run;
shasum -a 256 file-name
Your windows should have the utility 'CertUtil' installed, open terminal in your download directory or where ever you have the file stored and run;
CertUtil -hashfile file-name SHA256
The SHA256 should be displayed,compare this to what the site says, if different the file is corrupt or has been modified somehow.
There are also some GUI utilities available have a look at;