¡¾wait on line¡¿weird question about svnsync

dear subversion:
I have a weird question about svnsync:
i svnsync gzrepos(centos 6.4-svn1.6.11) to gz-mirror1(centos 7-svn1.9.5),
when it was done successfully, i found that the mirror repo(gz-mirror1) is more less than source repo(gzrepos) in sizes ,the source repo(gzrepos) is 177G while the mirror one(gz-mirror1) is only 66G
for example: revision:2012,it seems to be compressed

svnsync logs:



however, the mirror repo(gz-mirror1) seems OK, we can access,checkout,show log etc.
i heard that subversion 1.9.5 has Optimized data format,but the gap is too large¡£
I'm a little worried about the data£¬may i ask why?
best wish