Hello,
There aren't any resolution options in the miniclient itself. You should be able to adjust the size of the miniclient like any normal application. If you aren't able to do that, you'll have to adjust the resolution options in your system settings to adjust the size of the miniclient. You might also try a different version of the miniclient if you're having problems with your current version. Which version are you using right now? Please let me know, thanks!