The gzip documentation says:
The @command{gzip} format represents the input size modulo
@math{2^32}, so the uncompressed size and compression ratio are listed
incorrectly for uncompressed files 4 GiB and larger. To work around
this problem, you can use the following command to discover a large
uncompressed file's true size:@example zcat file.gz | wc -c @end example
