LoadTest Max Errors Assertion

One of the Assertion of LoadTest is  Max Errors Assertion。

one of the settings is"Max Relative Errors : Relative maximum allowed number of errors for the specified TestStep, for example 0.2 will assert that at most 20% of the runs for the specified TestStep result in an error".

What is the "Relative maximum " , and what is the "0.2 will assert that at most 20% of the runs for the specified TestStep result in an error"?