nvram memory 5% lower on 138, can I get it back? RT-N16

Now using tomato-K26USB-1.28.RT-MIPSR2-138-AIO, same AIO on v132.

v132 to v138, cleared nvram, re-entered all info.
v132 nvram free 8%
v138 nvram free 3%

any idea what is usung the extra nvram?
any way to get it back?

Thanks!