The problem is caused by filter operator. Please go to admin->widgets, please change the "Query type" by "and" or "or" like screenshot.
In fact, that is default option.
If you select the black color, you can see black products. And if there is only 5 blue products in black product list, filter query value will be calculated again.
So blue number will be shown by 5. Anyway, please try the "query type" method.
In the other theme's filter, you can see the same result.
If you have the other questions, please let us know again.
Best Regards, C-Themes