No worries, all is fine:
-v --verbose
Verbose. Display the name and percentage reduction for each file compressed or decompressed.
So, you're seeing how much the file was compressed, not some progress of the action itself.
It can even show negative values. Like if you wanted to test for yourself, and for that first generate a binary test file with random values, which is hard to compress:
$ head -c 100000 /dev/urandom > test.orig
$ file test.orig
test.orig: data
...and compress, which yields a file that is larger than the original:
$ gzip --keep test.orig
$ ls -l test.*
-rw-r--r-- 1 arjan staff 100000 Oct 18 11:36 test.orig
-rw-r--r-- 1 arjan staff 100063 Oct 18 11:36 test.orig.gz
...and decompress that, you'll see the funny negative value:
$ gzip -dcv test.orig.gz > test.new
test.orig.gz: -0.1%
But even then all is fine, as the following shows no differences:
$ diff test.orig test.new
Finally, you can also use --list
to see the (negative) compression ratio:
$ gzip --list test.orig.gz
compressed uncompressed ratio uncompressed_name
100063 100000 -0.1% test.orig
(Above output from OS X on a Mac.)