Well, yes, that's right! take a look at the tar file format here, specifically at the 'USTAR format':
So at +265 you have the 'Owner user name' and at +297 'Owner group name'.
let's try it:
yes, 'hernan' , that's me, 'wheel', yes, that's the group name.
Now go to google and do some 'filetype:tar'/'filetype:tgz' etc. searches
and have fun!. :)