Incorrect doubled meta title on homepage

HI,
I’m using the default wordpress theme twentyeleven.

This is what is set in the plugins “title & meta” for home:

%%sitedesc%% %%sep%% %%sitename%%

But at my home the title looks like this:

sitedesc sep (chosen by seo) sitenamesitename | sitedesc

so the problem is the repetition of the last part of the title.

Would be very happy for any help,
thanks!

https://www.ads-software.com/plugins/wordpress-seo/