Hi,
Thank you for letting us know about the issue with the rate which should indeed be 24%. We've updated the plugin.
Note that the tax rate plugin doesn't have a vocation to include all tax rates of all countries.
It only include the tax rates for electronic goods as they need to be taxed in the country of the buyer and thus, you need to enter all the main tax rates of all the countries in Europe.
For other type of goods, you normally apply the tax rate of your own country and thus you only have to enter a few tax rules/rates that you can easily enter through the interface in the backend.