The phrase “this much” is explained here: https://ell.stackexchange.com/questions/272326/what-does-i-know-this-much-is-true-mean
The Russian translation of this book title is: "Я знаю что это правда". The meaning of "this much" was lost in translation — as if the title was "I know this is true".
What would the Russian equivalent of "this much" be in this context?